Aspartame Intake Delayed Puberty Onset in Female Offspring Rats and Girls

SCOPE

The disturbance of the hypothalamic-pituitary-gonadal (HPG) axis, gut microbiota (GM) community, and short-chain fatty acids (SCFAs) is a triggering factor for pubertal onset. The study investigates the effects of the long-term intake of aspartame on puberty and GM in animals and humans.

METHODS AND RESULTS

Aspartame-fed female offspring rats result in vaginal opening time prolongation, serum estrogen reduction, and serum luteinizing hormone elevation. , 60 mg kg-1 aspartame treatment decreases the mRNA levels of gonadotropin-releasing hormone (GnRH), Kiss1, and G protein-coupled receptor 54 (GPR54), increases the mRNA level of RFamide-related peptide-3 (RFRP-3), and decreases the expression of GnRH neurons in the hypothalamus. Significant differences in relative bacterial abundance at the genus levels and decreased fecal SCFA levels are noted by 60 mg kg-1 aspartame treatment. Among which, Escherichia-Shigella is negatively correlated with several SCFAs. In girls, high-dose aspartame consumption decreases the risk of precocious puberty.

CONCLUSIONS

Aspartame reduces the chance of puberty occurring earlier than usual in female offspring and girls. Particularly, 60 mg kg-1 aspartame-fed female offspring delays pubertal onset through the dysregulation of HPG axis and GM composition by inhibiting the Kiss1/GPR54 system and inducing the RFRP-3. An acceptable dose of aspartame should be recommended during childhood.

The role of acid-labile subunit (ALS) in the modulation of GH-IGF-I action

Acid-labile subunit (ALS) deficiency (ACLSD) constitutes the first monogenic defect involving a member of the Insulin-like Growth Factor (IGF) binding protein system. The lack of ALS completely disrupts the circulating IGF system. Autocrine/paracrine action of local produced IGF-I could explain the mild effect on growth. In the present work we have revised the more relevant clinical and biochemical consequences of complete ACLSD in 61 reported subjects from 31 families. Low birth weight and/or length, reduced head circumference, height between -2 and -3 SD, pubertal delay and insulin resistance are commonly observed. Partial ACLSD could be present in children initially labeled as idiopathic short stature, presenting low IGF-I levels, suggesting that one functional IGFALS allele is insufficient to stabilize ternary complexes. Dysfunction of the GH-IGF axis observed in ACLSD may eventually result in increased risk for type-2 diabetes and tumor progression. Consequently, long term surveillance is recommended in these patients.

Ablating astrocyte insulin receptors leads to delayed puberty and hypogonadism in mice

Insulin resistance and obesity are associated with reduced gonadotropin-releasing hormone (GnRH) release and infertility. Mice that lack insulin receptors (IRs) throughout development in both neuronal and non-neuronal brain cells are known to exhibit subfertility due to hypogonadotropic hypogonadism. However, attempts to recapitulate this phenotype by targeting specific neurons have failed. To determine whether astrocytic insulin sensing plays a role in the regulation of fertility, we generated mice lacking IRs in astrocytes (astrocyte-specific insulin receptor deletion [IRKOGFAP] mice). IRKOGFAP males and females showed a delay in balanopreputial separation or vaginal opening and first estrous, respectively. In adulthood, IRKOGFAP female mice also exhibited longer, irregular estrus cycles, decreased pregnancy rates, and reduced litter sizes. IRKOGFAP mice show normal sexual behavior but hypothalamic-pituitary-gonadotropin (HPG) axis dysregulation, likely explaining their low fecundity. Histological examination of testes and ovaries showed impaired spermatogenesis and ovarian follicle maturation. Finally, reduced prostaglandin E synthase 2 (PGES2) levels were found in astrocytes isolated from these mice, suggesting a mechanism for low GnRH/luteinizing hormone (LH) secretion. These findings demonstrate that insulin sensing by astrocytes is indispensable for the function of the reproductive axis. Additional work is needed to elucidate the role of astrocytes in the maturation of hypothalamic reproductive circuits.

The Genetic Basis of Delayed Puberty

The genetic control of puberty remains an important but mostly unanswered question. Late pubertal timing affects over 2% of adolescents and is associated with adverse health outcomes including short stature, reduced bone mineral density, and compromised psychosocial health. Self-limited delayed puberty (DP) is a highly heritable trait, which often segregates in an autosomal dominant pattern; however, its neuroendocrine pathophysiology and genetic regulation remain unclear. Some insights into the genetic mutations that lead to familial DP have come from sequencing genes known to cause gonadotropin-releasing hormone (GnRH) deficiency, most recently via next-generation sequencing, and others from large-scale genome-wide association studies in the general population. Investigation of the genetic control of DP is complicated by the fact that this trait is not rare and that the phenotype is likely to represent a final common pathway, with a variety of different pathogenic mechanisms affecting the release of the puberty "brake." These include abnormalities of GnRH neuronal development and function, GnRH receptor and luteinizing hormone/follicle-stimulating hormone abnormalities, metabolic and energy homeostatic derangements, and transcriptional regulation of the hypothalamic-pituitary-gonadal axis. Thus, genetic control of pubertal timing can range from early fetal life via development of the GnRH network to those factors directly influencing the puberty brake during mid-childhood.

Clinical and biochemical characteristics and bone mineral density of homozygous, compound heterozygous and heterozygous carriers of three novel IGFALS mutations

OBJECTIVE

Acid-labile subunit (ALS) deficiency (ACLSD), caused by homozygous or compound heterozygous IGFALS mutations, is associated with moderate short stature, delayed puberty, low serum IGF-I and ALS and extremely low serum IGFBP-3. Its effect on birth weight, head circumference, bone mineral density (BMD), serum IGF-II and IGFBP-2 is uncertain, as well as the phenotype of heterozygous carriers of IGFALS mutations (partial ACLSD).

DESIGN

From all available members of five Turkish families, carrying three mutations in exon 2 of IGFALS (c.1462G > A, p.Asp488Asn (families A, B, E); c.251A > G, p.Asn84Ser (families C and E) and c.1477del, p.Arg493fs (family D)), clinical, laboratory and BMD data were collected.

METHODS

Auxological and biochemical findings were expressed as SDS for age and gender. Ternary complex formation in serum was investigated by size-exclusion chromatography. BMD using DXA bone densitometry was adjusted for height and age (Ha-BMD z-score).

RESULTS

In ACLSD (n = 24), mean ± s.d. height SDS (-2.7 ± 1.2), head circumference SDS (-2.3 ± 0.5) and body mass index (BMI) (-0.6 ± 1.0 SDS) were lower than those in partial ACLSD (n = 26, P ≤ 0.01) and birth weight SDS (n = 7) tended to be lower (-2.2 ± 1.1 vs -0.6 ± 0.3 in partial ACLSD (P = 0.07)). Serum IGF-I was -3.7 ± 1.4 vs -1.0 ± 1.0, IGF-II: -5.6 ± 0.7 vs -1.3 ± 0.7, ALS: <-4.4 ± 1.2 vs -2.1 ± 0.9 and IGFBP-3: -9.0 ± 1.9 vs -1.6 ± 0.8 SDS respectively (P < 0.001). Ha-BMD z-score was similar and normal in both groups.

CONCLUSIONS

To the known phenotype of ACLSD (i.e. short stature, reduced serum levels of IGF-I and ALS, extremely low serum IGFBP-3 and disturbed ternary complex formation), we add reduced birth weight, head circumference and serum IGF-II.

Discovery of a Genetic Metabolic Cause for Mauriac Syndrome in Type 1 Diabetes

A mechanistic cause for Mauriac syndrome, a syndrome of growth failure and delayed puberty associated with massive liver enlargement from glycogen deposition in children with poorly controlled type 1 diabetes, is unknown. We discovered a mutation in the catalytic subunit of liver glycogen phosphorylase kinase in a patient with Mauriac syndrome whose liver extended into his pelvis. Glycogen phosphorylase kinase activates glycogen phosphorylase, the enzyme that catalyzes the first step in glycogen breakdown. We show that the mutant subunit acts in a dominant manner to completely inhibit glycogen phosphorylase kinase enzyme activity and that this interferes with glycogenolysis causing increased levels of glycogen in human liver cells. It is known that even normal blood glucose levels physiologically inhibit glycogen phosphorylase to diminish glucose release from the liver when glycogenolysis is not needed. The patient's mother possessed the same mutant glycogen phosphorylase kinase subunit, but did not have diabetes or hepatomegaly. His father had childhood type 1 diabetes in poor glycemic control, but lacked the mutation and had neither hepatomegaly nor growth failure. This case proves that the effect of a mutant enzyme of glycogen metabolism can combine with hyperglycemia to directly hyperinhibit glycogen phosphorylase, in turn blocking glycogenolysis causing the massive liver in Mauriac disease.

Loss-of-function mutations in PNPLA6 encoding neuropathy target esterase underlie pubertal failure and neurological deficits in Gordon Holmes syndrome

CONTEXT

Gordon Holmes syndrome (GHS) is characterized by cerebellar ataxia/atrophy and normosmic hypogonadotropic hypogonadism (nHH). The underlying pathophysiology of this combined neurodegeneration and nHH remains unknown.

OBJECTIVE

We aimed to provide insight into the disease mechanism in GHS.

METHODS

We studied a cohort of 6 multiplex families with GHS through autozygosity mapping and whole-exome sequencing.

RESULTS

We identified 6 patients from 3 independent families carrying loss-of-function mutations in PNPLA6, which encodes neuropathy target esterase (NTE), a lysophospholipase that maintains intracellular phospholipid homeostasis by converting lysophosphatidylcholine to glycerophosphocholine. Wild-type PNPLA6, but not PNPLA6 bearing these mutations, rescued a well-established Drosophila neurodegenerative phenotype caused by the absence of sws, the fly ortholog of mammalian PNPLA6. Inhibition of NTE activity in the LβT2 gonadotrope cell line diminished LH response to GnRH by reducing GnRH-stimulated LH exocytosis, without affecting GnRH receptor signaling or LHβ synthesis.

CONCLUSION

These results suggest that NTE-dependent alteration of phospholipid homeostasis in GHS causes both neurodegeneration and impaired LH release from pituitary gonadotropes, leading to nHH.

Association between lead and cadmium and reproductive hormones in peripubertal U.S. girls

BACKGROUND

Lead (Pb) and cadmium (Cd) are known reproductive toxicants thought to disrupt hormone production throughout sensitive developmental windows, although this has not been previously examined in nationally representative peripubertal children.

OBJECTIVES

We examined the association between blood Pb and urinary Cd concentrations and the reproductive hormones inhibin B and luteinizing hormone (LH) in girls 6-11 years of age who participated in the cross-sectional Third National Health and Nutrition Examination Survey (NHANES III) (1988-1994).

METHODS

Pb (micrograms per deciliter) was measured in whole blood, and Cd was measured in urine (nanograms per milliliter). Inhibin B (picograms per milliliter) and LH (milli-International units per milliliter) were measured in residual sera for 705 girls. Survey logistic regression was used to estimate associations with pubertal onset based on inhibin B concentration > 35 pg/mL or LH concentration > 0.4 mIU/mL, and multinomial logistic regression was used to estimate the association between Pb and increasing categories of hormone concentrations.

RESULTS

High Pb (≥ 5 µg/dL) was inversely associated with inhibin B > 35 pg/mL [odds ratio (OR) = 0.26; 95% confidence interval (CI), 0.11-0.60; compared with Pb < 1 µg/dL]. At 10 and 11 years of age, girls with low Pb (< 1 µg/dL) had significantly higher inhibin B than did girls with moderate (1-4.99 µg/dL) or high Pb (≥ 5 µg/dL). In the subsample of 260 girls with levels of inhibin B above the level of detection and using survey regression modeling, inhibin B levels were lower among girls with both high Pb and high Cd (ß= -0.52; 95% CI, -0.09 to -1.04) than among girls with high Pb alone (ß= -0.35; 95% CI, -0.13 to -0.57), relative to girls with low Pb and low Cd.

CONCLUSIONS

Higher Pb was inversely associated with inhibin B, a marker of follicular development, and estimated effects suggestive of pubertal delays appeared to be stronger in the context of higher Cd concentrations. These data underscore the importance of Pb and Cd as reproductive toxicants for young girls.

Delayed puberty in spontaneously hypertensive rats involves a primary ovarian failure independent of the hypothalamic KiSS-1/GPR54/GnRH system

Spontaneously hypertensive (SH) rats, extensively used as experimental models of essential human hypertension, display important alterations in the neuroendocrine reproductive axis, which manifest as markedly delayed puberty onset in females but whose basis remains largely unknown. We analyze herein in female SH rats: 1) possible alterations in the expression and function of KiSS-1/GPR54 and GnRH/GnRH-receptor systems, 2) the integrity of feedback mechanisms governing the hypothalamic-pituitary-ovarian axis, and 3) the control of ovarian function by gonadotropins. Our data demonstrate that, despite overtly delayed puberty, no significant decrease in hypothalamic KiSS-1, GPR54, or GnRH mRNA levels was detected in this strain. Likewise, in vivo gonadotropin responses to ovariectomy and systemic kisspeptin-10 or GnRH administration, as well as in vitro gonadotropin responses to GnRH, were fully preserved in SH rats. Moreover, circulating LH levels were grossly conserved during prepubertal maturation, whereas FSH levels were even enhanced from d 20 postpartum onwards. In striking contrast, ovarian weight and hormone (progesterone and testosterone) responses to human chorionic gonadotropin (CG) in vitro were profoundly decreased in SH rats, with impaired follicular development and delayed ovulation at puberty. Such reduced hormonal responses to human CG could not be attributed to changes in LH/CG or FSH-receptor mRNA expression but might be linked to blunted P450scc, 3beta-hydroxy steroid dehydrogenase, and aromatase mRNA levels in ovaries from SH rats. In conclusion, our results indicate that the expression and function of KiSS-1/GPR54 and GnRH/GnRH-receptor systems is normal in SH rats, whereas ovarian development, steroidogenesis, and responsiveness to gonadotropins are strongly compromised.

The genetics of hypogonadotropic hypogonadism

An up-to-date review of the genetic aspects of idiopathic hypogonadotropic hypogonadism (IHH)/Kallmann syndrome (KS) is presented. Because proper development of the neuroendocrine axis must occur for normal puberty and reproductive function, gonadotropin-releasing hormone (GnRH) neuron migration is outlined first, followed by an introduction to the in vitro analysis of GnRH neuron migration. The normal hypothalamic-pituitary-gonadal (HPG) axis at different ages is discussed, along with a brief overview of normal and delayed puberty in both boys and girls. The phenotype of IHH/KS is discussed in detail, with its relation to Mendelian inheritance and chromosomal translocations. The molecular basis of IHH/KS is reviewed, with particular emphasis on the three most common genes ( KAL1, FGFR1, and GNRHR) that possess mutations in these patients. However, all other known genes for which mutations occur are also addressed briefly. The goal of this review is to provide a comprehensive discussion of IHH/KS, and to include both basic science and clinical findings that should allow a more complete understanding of hypothalamic-pituitary neuroendocrinology that is important in puberty and reproduction.

Tandem duplication ofDMD exon 18 associated with epilepsy, macroglossia, and endocrinologic abnormalities

We describe a patient with Duchenne muscular dystrophy (DMD) who additionally suffered from intractable seizures, severe mental retardation, and a marked macroglossia. He also had endocrinologic abnormalities consisting of growth hormone deficiency, delayed puberty, and adrenal hypoplasia. We detected a duplication of DMD exon 18 and flanking introns that caused a frame-shift and was not removed by corrective splicing. A coincident mutation in the FKRP gene was excluded by direct sequencing. Complex DNA rearrangements, deletions, and duplications >100 kb were excluded through microarray-comparative genomic hybridization (CGH), although we were not able to exclude a second coincident mutation with certainty. In conclusion, we present a case of DMD that conflicts with current understanding of genotype-phenotype relations and discuss putative pathogenetic mechanisms for this uncommon phenotype.

Evidence for hypermetabolism in boys with constitutional delay of growth and maturation

CONTEXT

Children with constitutional delay of growth and maturation (CDGM) tend to be thin and have a growth pattern reminiscent of nutritional insufficiency.

OBJECTIVE

Our objective was to compare differences in nutrition, body composition, bone mineral density, and resting and total energy expenditure (REE/TEE) in boys with CDGM and controls. We hypothesized that an imbalance between energy intake and expenditure may contribute to the pathogenesis of CDGM.

DESIGN AND SETTING

We conducted an observational, cross-sectional study at an outpatient clinical research center.

PATIENTS

Patients included 36 boys (8-17 yr): 12 with CDGM (short stature, delayed bone age and puberty, and no other pathology) and 12 height-matched (pre- or early-pubertal) and 12 age-matched (pubertal) healthy controls.

MAIN OUTCOME MEASURES

Outcome measures included doubly labeled water studies (TEE), serum nutritional/hormonal markers, dual-energy x-ray absorptiometry, dietary analysis, and indirect calorimetry (REE).

RESULTS

Nutritional markers were comparable among the groups. CDGM subjects had bone mineral density lower than age-matched controls (P < 0.01) but comparable with height-matched controls. Even though REE did not differ between groups, CDGM subjects had 25% higher caloric intake adjusted for fat-free mass (FFM) than height-matched controls (P < 0.05) and 78% higher caloric intake per kilogram FFM compared with age-matched controls (P < 0.00001). CDGM subjects had 46% (P < 0.05) and 91% (P < 0.001) higher TEE per kilogram FFM than height- and age-matched controls, respectively. CDGM subjects had lower IGF-I and testosterone than age-matched controls (P < 0.001) but levels were comparable with height-matched controls.

CONCLUSIONS

Boys with CDGM have higher rates of overall energy expenditure compared with age- and size-matched controls. This increased metabolism may result in impaired tempo of growth. Additional studies are needed to determine whether augmenting nutrition to match their energy needs (with or without hormonal therapy) can improve linear and ponderal growth in patients with CDGM.

IGF-1 administration to prepubertal female rats can overcome delayed puberty caused by maternal Pb exposure

Because prepubertal female rats maternally exposed to lead (Pb) exhibit suppressed serum levels of insulin-like growth factor-1 (IGF-1) and delayed puberty, we investigated the ability of centrally administered IGF-1 to stimulate luteinizing hormone (LH) release in vivo and LH-releasing hormone (LHRH) release in vitro from maternally Pb-exposed prepubertal female rats. Additionally, we assessed whether IGF-1 replacement could affect the timing of female puberty. Results demonstrated that IGF-1 stimulated significantly LH release in both control and Pb-exposed animals. When median eminences from control and Pb-exposed females were incubated with rat IGF-1 in vitro, they responded similarly with significant peptide-induced LHRH release. Lastly, we showed IGF-1 replacement reversed the delay in puberty caused by Pb. These results indicate the central LHRH response to IGF-1 is intact and that Pb-induced delayed puberty is due, at least in part, to suppressed circulating IGF-1 available to the hypothalamus.

Bone mineral density and markers of bone turnover in boys with constitutional delay of growth and puberty

It has been suggested that poor growth in childhood or puberty might be a correctable determinant of osteoporosis. To assess the effect of the growth and puberty delay on bone metabolism, we measured bone mineral density (BMD) and markers of bone turnover in 41 boys with constitutional delay of growth and puberty. Total body (TB) and lumbar spine (LS) BMD were measured by dual-energy x-ray absorptiometry. Serum osteocalcin, total alkaline phosphatase, and urinary deoxypyridinoline cross-links as markers of bone turnover were evaluated. BMD was decreased by at least 1 sd in TB in 23 boys (56%) and in LS in 27 boys (66%). After adjustment of BMD for bone age, TB was decreased in 11 boys (27%) and LS in 13 boys (32%). Bone age and chronological age significantly correlated with areal and volumetric BMD. The significant increments of height, weight, TB, and LS BMD between the consecutive pubertal stages were reported. Mean alkaline phosphatase, osteocalcin, and deoxypyridinoline were within reference ranges and showed no differences between pubertal stages. In conclusion, in boys with constitutional delay of growth and puberty, bone turnover is normal, and BMD increases in a manner similar to healthy children.

Pubertal upregulation of erythropoiesis in boys is determined primarily by androgen

OBJECTIVES

To study the relative roles of androgens and the growth hormone-insulin-like growth factor I (GH-IGF-I) system in the regulation of erythropoiesis in boys during puberty.

STUDY DESIGN

We treated 23 boys with constitutional delay of puberty with low-dose testosterone (T), in combination with either a potent aromatase inhibitor, letrozole (Lz; 2.5 mg/d), or placebo (P). The study design was randomized, double-blinded, and placebo-controlled between the treated groups. Treatment with T + Lz was associated with high T and low IGF-I concentrations, whereas treatment with T + P resulted in moderately increased T and high IGF-I concentrations.

RESULTS

The blood hemoglobin concentration increased by 1.6 g/dL in T + Lz-treated boys, despite their low IGF-I concentrations. The estimated red blood cell volume increased more in T + Lz-treated than in T + P-treated boys (349 vs 174 mL, respectively, P = .01). Serum T concentrations during the treatment period correlated with the 12-month increments in hemoglobin and red blood cell volume. The changes in blood hemoglobin concentration and RBC in T + Lz-treated boys were similar to those we observed in a population of normal adolescent boys in the late stages of puberty.

CONCLUSIONS

The pubertal increase in hemoglobin concentration in boys is related to direct androgen effects.

Augmentation of growth hormone secretion after testosterone treatment in boys with constitutional delay of growth and adolescence: evidence against an increase in hypothalamic secretion of growth hormone-releasing hormone

The increase in pituitary GH secretion that occurs during mid-late puberty in boys follows an increase in circulating testosterone (T) concentration; the direct mechanism by which this occurs is unknown. We hypothesized that T increases GH secretion during puberty by augmenting hypothalamic output of GHRH. Using constant infusions of a GHRH antagonist, we tested this hypothesis in six early pubertal boys with constitutional delay of growth and adolescence who had a mean chronological age of 14.0 +/- 0.3 yr and mean bone age of 11.4 +/- 0.2 yr. Blood samples were obtained from subjects every 15 min for 24 h during the overnight infusion of normal saline (2000-0600 h) and again during the overnight infusion of GHRH antagonist (0.33 microg/kg/h) the following night. Subjects then received transdermal T (5-mg patch) for 12 h nightly and were studied again after 4 wk of treatment. Serum samples were assayed for GH and total ghrelin; the percent suppression of GH during GHRH antagonist infusion was calculated. Morning serum T rose from 0.44 +/- 0.09 to 4.43 +/- 0.74 microg/liter (P = 0.005). T treatment was associated with a 92.6% increase in mean nocturnal GH secretion area under the curve (830 +/- 177 to 1599 +/- 340 microg/24 h.liter). Infusion of GHRH-antagonist suppressed mean nocturnal GH area under the curve by 29.1% before T treatment (830 +/- 177 to 621 +/- 168 microg/24 h.liter), and by 29.4% after T treatment (1599 +/- 340 to 1182 +/- 249 microg/24 h.liter; P = 0.99). Somatotroph sensitivity to GHRH was tested with 0.1- and 1.0-microg/kg doses of GHRH-44 iv; GH response did not change with regard to T treatment. The mean 24-h concentration of total ghrelin was unchanged with regard to T treatment. In summary, nightly transdermal T administration in six boys with constitutional delay of growth and adolescence increased GH output almost 2-fold, whereas the degree of GH suppressibility by GHRH antagonist remained unchanged. We conclude that the T-associated augmentation of GH secretion during early puberty in boys is unlikely to involve an absolute increase in hypothalamic GHRH output.

Effect of nutritional stress on the hypothalamo-pituitary-gonadal axis in the growing male rat

BACKGROUND/OBJECTIVE

Nutritional dwarfing (ND) consists of a decrease in weight and height gain and delayed onset of puberty. The aim of the present investigation was to study the modifications induced in male rats by the nutritional stress of a mere 20% reduction in food intake which, however, started immediately after weaning.

MATERIALS AND METHODS

At weaning, male Wistar rats were divided into two groups: Control (C) and ND. C rats were fed ad libitum with a balanced rodent diet. ND received 80% of the diet consumed by C for 4 weeks (T4); then they were fed ad libitum for another 4 (T8) and 8 weeks (T12). The rats were studied at T0, T4, T8 and T12 for the effects of nutritional stress and refeeding on nutritional status, body composition, hypothalamic-pituitary-gonadal axis, and sperm morphology and concentration.

RESULTS

ND body weight and length diminished vs. C (p < 0.001). ND body fat percentage decreased 40% (p < 0.001) without change in the percentage of body protein content. The hypothalamic content of LHRH did not change. However, FSH, LH and testosterone serum levels had significantly decreased (p < 0.001) at T4 in ND rats. A 48.4 % decrease in serum leptin in the ND group was observed at T4 (p < 0.05). The absolute testicular and seminal vesicle weight was significantly decreased by ND at T4 (p < 0.001). At T4 the percentage of anomalies of caudal spermatozoa increased in about 64% (p < 0.001) of ND vs. C rats, despite the unchanged sperm concentrations. All parameters normalized during refeeding.

CONCLUSION

In this model, a decrease in leptin due to nutritional stress could be responsible, at least in part, for the inhibition of reproductive function. Refeeding normalized all parameters studied.

Effect of low-dose testosterone treatment on androgen regulated proteins prostate specific antigen and sex hormone binding globulin in short prepubertal boys: lack of initiation of puberty

The efficacy of testosterone undecanoate (TU) treatment in constitutional delay of growth (CHD) is well recognized. We investigated its role in initiating puberty. Sera taken prior to, just after 6 months on and after 6 months off treatment with TU (20 mg daily) were analyzed from eight boys and compared to results from eight boys receiving placebo. Prostate specific antigen (PSA) and sex hormone binding globulin (SHBG), sleep-entrained pulsatility and mean overnight luteinizing hormone (mLH), and morning testosterone (T) levels were measured. Free androgen index (FAI) was calculated. Testicular volume (TV) and growth parameters were assessed. During treatment, there was a significant increase in height velocity in boys taking TU vs placebo (mean +/- SD: 5.7 +/- 2.0 vs 3.2 +/- 0.9 cm/year, p = 0.008) but no significant differences were observed in regard to LH pulsatility, mLH, T, SHBG, FAI, PSA and TV values. PSA was detectable in four patients (two each in the TU and placebo groups) at 6 months off treatment indicating pubertal progression. Among the hormones measured, only pretreatment mLH levels were significantly higher in the PSA-positive patients compared to 12 PSA-negative patients (mean +/- SEM: 1.5 +/- 0.39 vs 0.37 +/- 0.06 IU/l, p < 0.001). In conclusion, TU treatment shows no significant effect on initiation or advancement of puberty despite its resultant growth acceleration. Among the hormonal changes studied, mLH levels were the earliest indicator of pubertal initiation.

Puberty is delayed in male growth hormone receptor gene-disrupted mice

The role of insulin-like growth factor-I (IGF-I) in the initiation of puberty and testicular function is poorly understood. Growth hormone (GH) receptor (R) gene-disrupted mice or GHR gene "knockouts" (GHR-KO) are GH resistant and IGF-I deficient. To assess whether the age of sexual maturation is affected by the absence of IGF-I, various parameters of sexual development including testicular and accessory reproductive organ weights, balanopreputial separation, germ cell development, and intratesticular testosterone levels were determined in normal and GHR-KO mice between the ages of 25 and 60 days. In addition, at 36 days of age, the testosterone response to luteinizing hormone (LH) treatment was assessed in these mice. The results indicate that the balanopreputial separation was delayed 5 days, and a significant increase in the weights of the seminal vesicles (SV) occurred later in GHR-KO mice than in normal animals (between 30 and 35 days and between 35 and 40 days, respectively). Also, the weights of testes and epididymii were significantly reduced in GHR-KO mice. The intratesticular testosterone levels and the testosterone response to LH treatment were attenuated in GHR gene-disrupted mice. Furthermore, elongated spermatids appeared later in the testes of GHR-KO mice than in the testes of normal mice. These results suggest that the absence of IGF-I secretion delays the normal course of sexual maturation in male GHR-KO mice, indicating that IGF-I plays an important role in the initiation of puberty in male mice.

Neonatal superior ovarian nerve transection disturbs the cyclic activity of the female rats

The neural pathway most related with ovarian steroidogenesis has been identified as the superior ovarian nerve (SON). This work constitutes the first study of the effects of early ovarian SON transection, which was performed in rats of 4 days of age (SON-t rats) to magnify the effects of the denervation. The rats were studied at the prepubertal (30 days), peripubertal (41 days) and adult cyclic in dioestrus (60 days) reproductive stages. The SON-t rats showed a delay of vaginal opening, a notable disruption of oestrous cyclicity, and a large number of corpora lutea. In all the stages, the circulating levels of FSH, prolactin and growth hormone were lower in SON-t rats than in controls, whereas LH did not vary. Serum androstenedione levels were higher in SON-t rats at 30 days and lower at 41 days, compared with control animals while no difference was observed at 60 days. Serum progesterone levels did not differ between control and SON-t, but serum oestradiol concentrations were higher in SON-t rats in all of the stages. At the peripubertal stage, there were fewer ovarian beta-adrenergic receptors in SON-t ovaries, associated with a rise in the ovarian content of norepinephrine, but no changes were observed in SON-t rats at 30 and 60 days with respect to the controls. The release of progesterone in vitro from luteal cell in SON-t rats at 60 days was reduced in basal condition and under ovine LH or FSH stimulation, when compared with control animals; while no difference was observed in presence of isoproterenol or androstenedione in the culture medium. In corpora lutea of SON-t rats at 60 days, no change was observed in the activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), but the activity of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) was reduced, suggesting abnormal luteolysis in spite of the large number of corpora lutea. The interruption of innervation at an early age by SON transection is very important in the regulation of ovarian development in prepubertal and cyclic rats. The functional changes observed in the ovary suggest a possible alteration in the hypothalamic-hypophyseal axis.

Osteopenia in exercise-associated amenorrhea using ballet dancers as a model: a longitudinal study

Few longitudinal studies have investigated the effects of amenorrhea and amenorrhea plus exercise on bone mineral density (BMD) of young women. We carried out a 2-yr comparison of dancers and nondancers, both amenorrheic and normal, that investigated the role of hypothalamic amenorrhea on bone in this context. We studied 111 subjects (mean age, 22.4 +/- 4.6 yr; age of menarche, 14.1 +/- 2.2 yr), including 54 dancers, 22 with hypothalamic amenorrhea, and 57 nondancers, 22 with hypothalamic amenorrhea. Detailed hormonal and nutritional data were obtained in all groups to determine possible causal relationship to osteoporosis. The amenorrheic groups, dancers and nondancers, both showed reduced BMD in the spine, wrist, and foot, which remained below controls throughout the 2 yr. Only amenorrheic dancers showed significant changes in spine BMD (12.1%; P < 0.05) but still remained below controls, and within this subgroup, only those with delayed menarche showed a significant increase. The seven amenorrheic subjects (three dancers and four nondancers) who resumed menses during the study showed an increase in spine and wrist BMD (17%; P < 0.001) without achieving normalization. Delayed menarche was the only variable that predicted stress fractures (P < 0.005), which we used as a measure of bone functional strength. Analysis of dieting and nutritional patterns showed higher incidence of dieting behavior in this group, as manifested by higher Eating Attitudes Test scores (16.3 +/- 2.00 vs. 11.5 +/- 1.45; P < 0.05) and higher fiber intakes (30.7 +/- 3.00 vs. 17.5 +/- 2.01 g/24 h; P < 0.001). We concluded that low bone mass occurs in young women with amenorrhea and delayed menarche, both exercisers and nonexercisers. Crucial bone mass accretion may be compromised by their reproductive and nutritional health.

Delayed puberty

Normal puberty is a time of life and a process of development that results in full adult maturity of growth, sexual development, and psychosocial achievement. Delayed puberty describes the clinical condition in which the pubertal events start late (usually > +2.5 SD later than the mean) or are attenuated in progression. The differential diagnosis includes syndromes of low gonadotropin production, usually constitutional delay of growth and maturation associated with chronic disease, but also an array of gene-mediated disorders, and syndromes of primary gonadal dysfunction with hypergonadotropic hypogonadism, including Turner and Klinefelter syndromes, and a group of acquired and genetic abnormalities. Diagnostic assessment and varied therapeutic modalities are discussed. The issues of androgen or estrogen therapy are important to assess, and growth hormone treatment remains a difficult dilemma.

[Evaluation of bone mineral density and selected metabolic markers of bone in boys with constitutional delay of growth and puberty]

The aim of this study was to evaluate bone mineral density and some markers of bone metabolism (alkaline phosphatase activity, osteocalcin concentration, deoxypirydinoline excretion), as well as the influence of physical activity and dietary calcium supplementation on bone density and bone metabolism in boys with a constitutional delay of growth and puberty (CDGP), in relation to calendar age, bone age and pubertal stage. The study was done in 41 boys aged 8-18 years with CDGP diagnosed on the basis of family history and typical pattern of growth, with prior exclusion of hormonal and non-hormonal causes of height deficiency. According to Tanner's criteria, boys were assigned to 4 groups corresponding to 4 stages of puberty (Tab. 1). Total body (total BMD) and lumbar spine (L2L4 BMD) bone mineral density were obtained using DEXA densitometry. The activity of alkaline phosphatase (AP) and serum osteocalcin (OC) concentration served as markers of bone formation. 24-h urinary deoxypirydinoline (DPD) excretion was a marker of bone resorption. Using a questionnaire, daily dietary calcium intake and physical activity were established. A positive correlation between calendar age, total BMD and L2L4 BMD was found (R = 0.70 and R2 = 0.49; R = 0.72 and R2 = 0.51; p < 0.001, respectively). Bone age was positively correlated with total BMD and L2L4 BMD (for both correlations R = 0.68, R2 = 0.47; p < 0.001). Total BMD adjusted for calendar age revealed osteoporosis in 4 cases (9.7%), osteopenia in 19 cases (46.3%) and normal bone density in 18 cases (43.9%). After adjustment of BMD to bone age, 2 boys (4.9%) were diagnosed with osteoporosis, 9 (21.9%) with osteopenia, and 30 (73.2%) with normal bone density. L2L4 BMD adjusted for calendar age showed osteoporosis in 6 cases (14.6%), osteopenia in 21 cases (51.2%) and normal density in 14 cases (34.2%). After adjustment of BMD to bone age, 3 boys (7.3%) were diagnosed with osteoporosis, 10 (24.4%) with osteopenia, and 28 (68.3%) with normal bone density. A significant correlation between stage of puberty, total BMD (p < 0.045) and L2L4 BMD (p < 0.001) was found. Values for total BMD and L2L4 BMD in boys with CDGP in relation to pubertal stage are presented in Table 2. Mean AP activity, serum OC concentration, DPD excretion, dietary calcium intake and physical activity in boys at consecutive stages of puberty are presented in Table 3. No significant correlation between pubertal stage, markers of bone metabolism, daily dietary calcium intake or physical activity was found. The boys were next grouped according to level of physical activity: low (< 10 h/week) or high (> 10 h/week). Table 4 summarizes the results for both groups. No significant differences between the groups were found concerning the parameters studied. Two groups with a low (< 1.2 g) and high (> 1.2 g) dietary calcium intake were also formed. The results for both groups are presented in Table 5. A significant correlation between dietary calcium intake and total BMD (R = 0.34 and R2 = 0.11; p < 0.03) was revealed. On the basis of these results it can be concluded that BMD values in boys with CDGP should be adjusted for bone age, thus significantly limiting the diagnosis of osteoporosis and osteopenia. BMD values for these boys increase with consecutive pubertal stage, while markers of bone metabolism do not reveal significant abnormalities (markers of bone formation increase until stage IV, markers of bone resorption show fluctuating values).

Dihydrotestosterone treatment in adolescents with delayed puberty: does it explain insulin resistance of puberty?

Puberty is characterized by temporary insulin resistance, which subsides with the completion of pubertal development. This insulin resistance is manifested by lower rates of insulin-stimulated glucose metabolism and compensatory hyperinsulinemia in pubertal compared with prepubertal children. Whether or not pubertal insulin resistance is the result of sex steroids or GH or a combination of both has been investigated in our laboratory. Previously, we demonstrated that T treatment in adolescents with delayed puberty was not associated with the deterioration of insulin action. The present investigation evaluated the effects of 4 months of dihydrotestosterone administration (50 mg im every 2 wk) on body composition, glucose, fat, and protein metabolism, and insulin sensitivity. Ten adolescents with delayed puberty were evaluated before and after 4 months of DHT administration. Body composition was assessed by dual energy x-ray absorptiometry. Insulin-stimulated glucose metabolism was measured during a 3-h hyperinsulinemic (40 mU/m(2).min)-euglycemic clamp procedure. Lipolysis and proteolysis were evaluated by stable isotopes of [(2)H(5)]glycerol and [1-(13)C]leucine. After 4 months of dihydrotestosterone treatment, height, weight, and fat free mass increased and percentage of body fat decreased. IGF-I and nocturnal GH levels did not change. There was no significant change in insulin-stimulated glucose metabolism (57.2 +/- 3.9 vs. 58.3 +/- 3.9 micromol/kg.min). Total body proteolysis and lipolysis did not change. In summary, based on the present and past studies, we conclude that during puberty insulin resistance/hyperinsulinemia is not attributable to gonadal sex steroids in boys.

[Selected markers of bone metabolism in boys with constitutional delay of growth and puberty]

The aim of the study was to determine serum concentration and urinary excretion of selected parameters of bone metabolism in boys with constitutional delay of growth and puberty (CDGP) in the relation to pubertal stages. The study group consisted of 41 boys (aged 8 to 18 yrs) with CDGP. Patients were divided on the basis of Tanner's criteria into 4 groups according to the pubertal stage. Serum alkaline phosphatase (AP) activity and serum osteocalcin (OC) concentration as markers of bone growth, as well as urinary deoxypyridinoline (DPD) as a marker of bone resorption were determined. Serum AP activity in 31 (75.6%) boys was within normal age range. Mean values of serum AP activity increased insignificantly from I to IV stage of puberty. Serum OC concentrations were normal in 33 (80.5%) patients. Eight (19.5%) boys showed decreased values of serum OC concentration. Mean OC concentration insignificantly increased with the pubertal stages. DPD urinary excretion was within normal age range in all patients and was the highest in stage III of pubertal stage. No significant abnormalities of bone metabolism parameters in boys with constitutional delay of growth and puberty were found.

Effects of delaying puberty on bone mineralization in female rats

The effect of delaying puberty on bone mineralization was studied using female rats as a model. Repeated injections of gonadotrophin-releasing hormone antagonist (GnRHa) were used to suppress the onset of puberty from the age of 6-10 weeks. A group of control female rats was given aqueous solution injections at the same age and for the same duration. The effect of delaying puberty on bone mineralization was examined using dual energy X-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (QCT), both methods being adapted for small animals. Bone mineral parameters were measured at baseline and at the ages of 10, 17 and 24 weeks in total body, femur and spine. Compared to controls, bone mineral content (BMC) and bone mineral density (BMD), as measured by DXA, were significantly decreased in GnRHa-treated rats in total body and femur at 10 and 24 weeks of age (P < 0.05). The results were even more significant after adjusting for weight. After this adjustment, spine BMC and BMD at 10, 17 and 24 weeks were significantly lower in the treatment group (P < 0.05). Trabecular BMD at the distal femur in the GnRHa treated group as measured by peripheral QCT was significantly lower (P < 0.05). However, cortical bone in the mid-femur had higher BMD, concurrent with lower cortical thickness in the treatment group. In conclusion, a delay in the onset of sexual maturation may cause prolonged, possibly irreversible defect in bone mineralization.

Spontaneous and GnRH-provoked gonadotropin secretion and testosterone response to human chorionic gonadotropin in adolescent boys with thalassaemia major and delayed puberty

To elucidate whether the cause of sexual maturation arrest in thalassaemia is of gonadal or pituitary etiology, 10 males with thalassaemia and delayed puberty and 10 with constitutional delay of growth and pubertal maturation (CSS) were extensively studied. Their spontaneous nocturnal gonadotropin secretion and gonadotropin response to intravenous 100 micrograms gonadotropin-releasing hormone (GnRH) were evaluated. Circulating testosterone concentration and clinical response were evaluated after 3 days, 4 weeks and 6 months of intramuscular administration of human chorionic gonadotropin (HCG) (2500 U/m2/dose). Thalassaemic boys had significantly lower circulating concentrations of testosterone compared to those with constitutional delay of growth and sexual maturation (CSS) at the same pubertal stage. Short- and long-term testosterone response to administrations of HCG was markedly decreased in thalassaemic boys. After 6 months of HCG administration 50 per cent (5/10) of the boys did not show significant testicular enlargement or genital changes. Despite the low circulating concentrations of testosterone, none of the patients had high basal or exaggerated gonadotropin response to gonadotropin releasing hormone (GnRH) stimulation. Luteinizing hormone (LH) peak responses to GnRH were significantly lower as compared to controls. Follicle-stimulating hormone (FSH) peak responses to GnRH did not differ among the two study groups. The mean nocturnal LH and FSH secretion was significantly decreased in all thalassaemic boys as compared to boys with CSS at the same pubertal stage (testicular volume). These data proved that hypogonadotropic hypogonadism is the main cause of delayed/failed puberty in adolescents with thalassaemia major. MRI studies revealed complete empty sella (n = 5), marked diminution of the pituitary size (n = 5), thinning of the pituitary stalk (n = 3) with its posterior displacement (n = 2), and evidence of iron deposition in the pituitary gland and midbrain (n = 8) in thalassaemic patients, denoting a high incidence of structural abnormalities (atrophy) of the pituitary gland. Moreover, in many of the thalassaemic boys, the defective testosterone response to long-term (6 months) HCG therapy denoted significant testicular atrophy and/or failure secondary to siderosis. It appears that testosterone replacement might be superior to HCG therapy in these patients. This therapy should be introduced at the proper time in these hypogonadal patients to induce their sexual development and to support their linear growth spurt and bone mineral accretion.

Could growth retardation in cystic fibrosis be partly due to deficient steroid and thyroid hormonogenesis?

Cystic fibrosis (CF) mainly affects Caucasians of northwestern-European ancestry with severe morbidity. The individuals are malnourished and growth retarded. The latter is thought to be the consequence of delayed maturation of the hypothalamic-pituitary-gonadal axis due to malnourishment. However, there is evidence that steroid and thyroid hormone syntheses may be impaired in CF. Thyrotropin stimulates the uptake and efflux of iodide before the halide is incorporated into thyroid hormones and it is becoming apparent that gonadotropins likewise mobilise chloride ions in Leydig cells prior to steroidogenesis. Since the primary defect causing CF is the mutated cystic fibrosis transmembrane conductance regulator (CFTR)--a chloride channel residing on the apical membrane of wet epithelia, the growth retardation in CF may in part be due to deficient hormone syntheses. The latter may involve CFTR or may be the halide channel activated by glycoprotein hormones prior to hormonogenesis.

Bone mineral status in prepubertal children with constitutional delay of growth and puberty

OBJECTIVE

We wished to clarify whether the osteopenia reported in adult men with a history of constitutional delay of growth and puberty (CDGP) could be due to the delayed puberty or an independent predisposition to osteoporosis in this condition.

DESIGN

Short prepubertal children with CDGP and children with familial short stature (FSS) were matched for height and other auxological variables. The FSS children served as a control group.

METHODS

We measured spinal (L1-L4) bone mineral content (BMC) and bone mineral density (BMD) by dual energy X-ray absorptiometry (Hologic QDR 1000/w) in 56 children aged 5-11 years. All children had height below the 10th percentile for chronological age (CA), and bone age (BA) less than 10 years, 29 of them with clinical diagnosis of possible CDGP and 27 of them with FSS. The BMD standard deviation scores (SDS) relative to the values for normal height children were obtained.

RESULTS

The mean (+/-S.D.) spinal BMD was significantly lower in the children with CDGP than in the FSS group (0.534+/-0.059 vs 0.623+/-0.060 g/cm2, P< 0.001). Both groups had negative mean lumbar BMD SDS, but in the CDGP group it was significantly lower than in the FSS group as well when the SDS was based on the CA (-1.41+/-0.61 vs -0.38+/-0.51, P< 0.001) and when it was related to BA (-0.78+/-0.64 vs -0.17+/-0.52, P< 0.01). BMC was significantly lower in the CDGP than in the FSS group, when multiple regression analysis was performed by using scanned bone area, body weight and height, sex and BA as independent variables (P = 0.0005).

CONCLUSION

The finding of decreased mineralization in prepubertal children with CDGP before the age of puberty suggests that they may have an inherent predisposition to osteopenia.

Testosterone treatment in adolescents with delayed puberty: changes in body composition, protein, fat, and glucose metabolism

Previously, we demonstrated decreased protein breakdown and insulin resistance in pubertal adolescents compared with prepubertal children. Puberty-related increases in sex steroids and/or GH could be potentially responsible. In the present study, the effects of 4 months of testosterone enanthate (50 mg in every 2 weeks) on body composition, protein, fat, and glucose metabolism and insulin sensitivity were evaluated in adolescents with delayed puberty. Body composition was assessed by H218O-dilution principle. Protein breakdown, oxidation, and synthesis were measured during primed constant infusion of [1-13C]leucine. Whole-body lipolysis was measured during primed constant infusion of [2H5]glycerol. Insulin action in suppressing proteolysis and lipolysis and stimulating glucose disposal was assessed during a stepwise hyperinsulinemic (10 and 40 mU-m2.min) euglycemic clamp. Fat and glucose oxidation rates were calculated from indirect calorimetry measurements. After 4 months of testosterone treatment, height, weight, and fat free mass (FFM) increased and fat mass, percent body fat, plasma cholesterol, high- and low-density lipoproteins, and leptin levels decreased significantly. Whole-body proteolysis and protein oxidation were lower after testosterone treatment (proteolysis, 0.49 +/- 0.03 vs 0.54 +/- 0.04 g.h.kg FFM, P = 0.032; oxidation, 0.05 +/- 0.01 vs. 0.09 +/- 0.01 g.h.kg FFM, P = 0.015). Protein synthesis was not different, and resting energy expenditure was not different. Total body lipolysis was not affected by testosterone treatment, however, fat oxidation was higher after testosterone (pre-: 2.4 +/- 0.7 vs. post-: 3.5 +/- 0.7 mumol.kg.min, P = 0.031). During the 40 mU.m2.min hyperinsulinemia, insulin sensitivity of glucose metabolism was not affected with testosterone therapy (59.1 +/- 8.8 vs. 57.1 +/- 8.2 mumol.kg.min per muU/mL). However, metabolic clearance rate of insulin was higher posttestosterone (13.6 +/- 1.1 vs. 16.7 +/- 0.8 mL.kg.min, P = 0.004). In conclusion, after 4 months of low-dose testosterone treatment in adolescents with delayed puberty 1) FFM increases and fat mass and leptin levels decrease; 2) postabsorptive proteolysis and protein oxidation decrease; 3) fat oxidation increases; and 4) insulin sensitivity in glucose metabolism does not change, whereas insulin clearance increases. These longitudinal observations are in agreement with our previous cross-sectional studies of puberty and demonstrate sparing of protein breakdown of approximately 1.2 g.kg.day FFM, wasting of fat mass, but no change in insulin sensitivity after short periods of low-dose testosterone supplementation.

[Delayed puberty]

Delayed puberty can be defined as the absence of any signs of puberty in subjects that have attained an age at the upper limit (+2DS) for the onset of puberty, that means 13 years in girls and 14 years in boys. The causes of delayed puberty can be classified into three groups, functional temporary impairment in gonadotropin and sex steroid secretion (most frequently constitutional delay of puberty), hypothalamo-pituitary failure with deficiency in gonadotropin secretion, primary gonadal failure with increased gonadotropin levels. The Authors discuss about etiology, diagnostic testing and therapeutic approach in these conditions. The majority of children with delayed puberty are males that have only a constitutional delay of growth and puberty. It is difficult, in teenage years, to distinguish this common and benign condition from true gonadotropin deficiency, in spite of the variety of endocrine tests developed for this purpose. Individuals with constitutional delayed puberty with a bone age greater than 11.5 years, show after triptorelin stimulation an increase in LH capable of distinguishing them from patients with gonadotropin deficiency. In our opinion this could be an important screening test to exclude gonadotropin deficiency in boys with delayed puberty.

Successful treatment of short stature and delayed puberty in congenital magnesium-losing kidney

Bartter's syndrome is a well described but uncommon disease characterized by hypokalaemia and hyperplasia of the juxtaglomerular apparatus of the kidney. It may present in infancy with failure to thrive and muscle weakness; it commonly causes short stature. Lesions at different sites within the renal tubule have been proposed as the cause of the syndrome. However, the biochemical abnormalities in many cases can be explained by defective reabsorption of chloride in the ascending loop of Henle, with loss of sodium and water and a secondary increase in renin and aldosterone concentrations. Less severe cases have been described which present in adolescence and have tetany as a prominent feature. Primary renal loss of magnesium associated with potassium wasting has been described in such cases and it has been suggested that these can be distinguished from classical Bartter's syndrome by hypocalciuria. This less well characterized disease has been named Welt, Gitelman-Welt or Gitelman syndrome and may include deficient tubular reabsorption of chloride, but the sites of magnesium and potassium loss in the kidney are uncertain. We describe a patient with this syndrome who presented with short stature, delayed puberty and tetany and responded well to magnesium replacement.

Androgen receptor blockade with flutamide enhances growth hormone secretion in late pubertal males: evidence for independent actions of estrogen and androgen

Exogenous and endogenous sex steroid hormones influence GH secretion. To test the relative importance of androgens in the enhancement of GH secretion, we administered flutamide (a potent androgen receptor blocker) to six late pubertal males. Blood samples for GH (and LH) were obtained at 10-min intervals for 24-h periods after 3 days of flutamide and during the untreated state. Waveform-specific, multiple-parameter deconvolution analysis was employed to assess secretory and elimination dynamics for GH. Androgen receptor blockade was confirmed by significant increases in 24-h mean LH concentrations and in total 17 beta-estradiol and free testosterone levels in the serum. Mean serum GH concentrations (24-h) also increased (P < 0.001) during androgen receptor blockade (mean +/- SEM, 2.9 +/- 0.3 vs. 1.8 +/- 0.3 micrograms/L); this was associated with an increased (P < 0.001) GH production rate [152 +/- 15 vs. 93 +/- 16 micrograms/liter of distribution volume (Lv)/24 h]. The enhanced GH secretion during flutamide administration was a result of both increased mass of GH released per secretory burst (12.0 +/- 1.4 vs. 8.4 +/- 1.0 micrograms/Lv; P < 0.005) and increased maximal rate of GH secretion (0.39 +/- 0.04 vs. 0.30 +/- 0.03 micrograms/Lv/min; P < 0.05), as well as a small increase in the number of detectable secretory bursts (12 +/- 1 vs. 10 +/- 1/24 h; P < 0.05). There was no significant change in either the serum half-life of GH or in the half-duration of GH secretory bursts during androgen receptor blockade. We speculate that the augmentation of GH secretion observed during antagonism of androgen action in late pubertal males is a result of increased stimulation of estrogen receptor-mediated pathways. Alternatively, androgens may exert a tonic inhibition of GH secretion which can be abolished by androgen receptor blockade.

The somatotropic axis in puberty

Sex steroids markedly affect GH pulsatility by altering GH pulse amplitude without affecting GH pulse frequency. The type of sex steroid (testosterone or estrogen) appears to determine the timing of the pubertal growth spurt although both steroids appear to influence the amount of GH released from the pituitary. GH levels also affect gonadal secretion of sex steroids. The effects of the two are synergistic, but there is a real therapeutic dilemma of what to increase and when in children who are deficient in either GH or gonadotrophin secretion. Augmented GH pulsatility, particularly during the day, may alter markedly the interpretation of standard endocrine tests. Finally, the insulin resistance arising from an increased circulating concentration of GH may have important implications for the management of insulin-dependent diabetes during puberty.

[Determination of growth hormone binding protein in a normal population and in subjects with short stature due to growth hormone resistance]

With the procedure which uses gel-filtration and high pressure liquid chromatography (HPLC) the authors measured the GH-binding proteins in 96 healthy subjects aged 6 months to 40 years. In the blood 45% of the GH is bound to the BP. The diagnosis was confirmed by our method in 13 patients with Laron type dwarfism and in four patients the GH receptor defect had been proved. The parents, the brothers and sisters showed significantly lower GH-BP II (principal GH-BP) levels. Possible regulation of GH-binding proteins in human plasma was examined. Eight children with isolated GH deficiency had a very low level of plasma GH binding activity (mean +/- SEM) (10.2 +/- 1.1% of radioactivity). Under GH treatment the hormone binding to high affinity BP (GH-BP II) increased in every patient to reach the mean value of 18.5 +/- 1.4%. This increase was related to a higher binding capacity without any significant change in the binding affinity. In nine boys with pubertal delay, the GH specific binding to peak II-BP (GH-BP II) was found to be normal (30.6 +/- 3.7%); it decreased significantly following testosterone treatment. In four boys with precocious puberty, the specific GH binding to peak II BP was low (16.6 +/- 1.1%). It increased significantly to 21.6 +/- 1.1% of radioactivity after treatment with LH-RH analogue. GH and testosterone have an opposite role in the regulation of the high affinity GH-BP.

Melatonin secretion during adrenarche in normal human puberty and in pubertal disorders

The relation between human melatonin secretion and adrenarche was investigated in 113 subjects ages 5.5-17 years. Melatonin nocturnal profile was determined obtaining hourly blood samples from 2000 to 0800 and DHEA-S was measured in pooled plasma of these samples. In 62 normal subjects, melatonin peak by stages of adrenarche was 152.5 +/- 65.4, 125.9 +/- 59.4, and 115.2 +/- 40.7 pg/ml for stages 1, 2, and 3-5, respectively, and the linear trend components were significant; no significant relation remained after partialling the variance associated with age and pubertal stages. In 41 subjects with disorders of pubertal onset, mean melatonin peak by stages of adrenarche was 149.0 +/- 54.4, 194.0 +/- 34.2, and 129.8 +/- 52.2 pg/ml for stages 1, 2, and 3-5, respectively, and the linear trend components were not significant. In seven prepubertal girls with precocious adrenarche, melatonin peak was not significantly different from values in seven normal prepubertal, preadrenarchal girls. The relation between time of melatonin peak and adrenarche was not significant in any of the diagnostic groups. The linear correlation between melatonin peak and DHEA-S was not significant in either adrenarche stage 1 (r = -0.19, n = 41) or stages 3-5 (r = -0.13, n = 23). The results do not support a role for adrenarche in the pineal-puberty relation in humans.

Osteopenia in men with a history of delayed puberty

BACKGROUND AND METHODS

The effect of delayed puberty on peak bone mineral density in men is unknown. To determine whether such a delay reduces normal peak bone density and leads to osteopenia during adulthood, we measured radial bone mineral density by single-photon absorptiometry and spinal bone mineral density by dual-energy x-ray absorptiometry in 23 men who had a history of constitutionally delayed puberty and 21 men who underwent normal puberty. Their mean ages were 26 and 24 years, respectively. The groups were matched for other factors known to affect bone mass.

RESULTS

The mean (+/- SD) radial bone mineral density was significantly lower in the men with a history of delayed puberty than in the normal men (0.73 +/- 0.07 vs. 0.80 +/- 0.05 g per square centimeter; P less than 0.0002). Spinal bone mineral density was also significantly lower in the men with delayed puberty than in the normal men (1.03 +/- 0.10 vs. 1.13 +/- 0.11 g per square centimeter; P less than 0.003). Radial bone density was at least 1 SD below the mean value for the normal men in 15 of the 23 men with a history of delayed puberty, and spinal bone density was similarly decreased in 10 of the 23.

CONCLUSIONS

Adult men with a history of constitutionally delayed puberty have decreased radial and spinal bone mineral density. These findings suggest that the timing of puberty is an important determinant of peak bone density in men. Because the peak bone mineral density achieved during young adulthood is a major determinant of bone density in later life, men in whom puberty was delayed may be at increased risk for osteoporotic fractures when they are older.

Testosterone and oxandrolone, a nonaromatizable androgen, specifically amplify the mass and rate of growth hormone (GH) secreted per burst without altering GH secretory burst duration or frequency or the GH half-life

We investigated the mechanisms by which androgens increase mean circulating GH concentrations in boys. We tested two hypotheses: 1) testosterone increases serum GH concentrations at least in part via an androgen receptor-mediated mechanism, rather than exclusively by way of aromatization to estrogen; 2) androgen augments one or more specific features to GH secretion (secretory burst number, amplitude, and/or duration) and/or prolongs the half-life of GH removal. To examine these hypotheses, prepubertal boys with constitutionally delayed development and/or growth were given injections of testosterone (100 mg monthly; n = 7) or treated with oral oxandrolone, a nonaromatizable androgen (1.25 mg twice daily; n = 5). Pulsatile GH release was studied before and during androgen administration by sampling blood at 20-min intervals for 24 h. The immunoreactive GH time series were subjected to a novel deconvolution technique, which revealed that 1) testosterone and oxandrolone each increased mean (24-h) serum GH concentrations significantly; 2) both androgens augmented the daily endogenous GH secretory rate significantly; 3) increased GH production resulted from a higher mass of GH secreted per burst and a higher maximal rate of GH secretion within each burst; and 4) androgens amplified the magnitude of the nyctohemeral rhythm in the mass (but not frequency) of GH secretory pulses. The observed effects of androgen were specific, since the number and duration of GH secretory bursts and the subject-specific GH half-life were unaltered by androgen treatment. We conclude that androgen acting apart from conversion to estrogen is capable of specifically activating the somatotropic axis via distinct neuroendocrine secretory mechanisms.

The metoclopramide test: a useful tool with the luteinizing hormone-releasing hormone test in distinguishing between constitutional delay of puberty and hypogonadotropic hypogonadism

To evaluate the effectiveness of intravenous metoclopramide, alone or in combination with luteinizing hormone-releasing hormone (LH-RH), in distinguishing between constitutional delay of puberty and hypogonadotropic hypogonadism, 12 patients with constitutional delay of puberty and 10 patients with hypogonadotropic hypogonadism were studied. All patients received 10 mg/m2 of intravenous metoclopramide and 100 micrograms of intravenous LH-RH on separate days. The mean prolactin (PRL) response following metoclopramide was significantly higher in the constitutional delay of puberty group when compared with the hypogonadotropic hypogonadism patients (P less than 0.01 at 15, 30, 45, and 60 minutes); all patients with constitutional delay of puberty increased their PRL level to greater than or equal to 60 ng/ml, except one who had a peak PRL level of 38 ng/ml. While only 2 of the hypogonadotropic hypogonadism subjects reached a peak PRL concentration of greater than or equal to 60 ng/ml, 4 had peak PRL levels greater than 38 ng/ml. The mean LH and follicle-stimulating hormone (FSH) responses after LH-RH were significantly higher in the constitutional delay of puberty group (P less than 0.01 at 30, 45, and 60 minutes for LH and P less than 0.01 at 45 and 60 minutes for FSH). All constitutional delay of puberty subjects responded to both the metoclopramide and LH-RH tests, while patients with hypogonadotropic hypogonadism responded only to one or to neither of these tests. Therefore, while metoclopramide alone did not allow us to clearly distinguish constitutional delay of puberty from hypogonadotropic hypogonadism, the combined use of both of these stimuli permitted us to detect all subjects with constitutional delay of puberty.

Effect of increased haemoglobin levels on growth hormone (GH) secretion in beta-thalassaemia major: differences between prepubertal subjects and patients with delayed puberty

Basal and L-dopa-stimulated secretion of growth hormone (GH) was investigated in 10 patients with beta-thalassaemia major. Five patients were prepubertal (chronological age 8 to 12 years), whereas 5 patients had delayed puberty (chronological age 15 to 19 years). Ten normal prepubertal subjects (chronological age 8 to 11 years) served as the control group. Each thalassaemic patient was subjected to two L-dopa tests (0.5 g L-dopa plus 0.7 mg/Kg body weight propranolol, orally): one was performed under conditions of low haemoglobin (Hb) levels (30 days after the last blood transfusion), and the second in the presence of increased Hb concentrations (10 days after the transfusion of packed red blood cells). Before the transfusion of packed red blood cells, basal GH concentrations were significantly higher in the patients with delayed puberty (4.3 +/- 1.6 ng/ml), than in prepubertal thalassaemic (1.8 +/- 0.9 ng/ml, p less than 0.05) and control (1.9 +/- 1.0 ng/ml, p less than 0.02) subjects. In contrast, the pituitary responsiveness to L-dopa, expressed as the relative maximum response for GH (GH delta %), was significantly higher in the latter two groups (8.5-fold, p less than 0.05, and 10.9-fold, p less than 0.02, respectively). The transfusion of packed red blood cells increased significantly Hb concentrations in both groups of thalassaemic patients (prepubertal +27%, p less than 0.05, delayed puberty +33%, p less than 0.025, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Responsiveness of gonadotropin secretion to infusion of an opiate-receptor antagonist in hypogonadotropic individuals

We tested the hypothesis that suppressive effects of endogenous opiate substances are involved in certain hypogonadotropic states. For this purpose, we studied gonadotropin secretion in idiopathic hypopituitarism (five children), constitutionally delayed adolescence (five boys), and Kallmann's syndrome (three men). Endogenous opiate pathways were antagonized by the iv infusion of naloxone hydrochloride at a dose previously shown to elicit a prompt and significant increase in serum levels of LH in normal men. Under these conditions, naloxone did not increase serially sampled serum concentrations or mean urinary levels of LH: or FSH in eight patients with idiopathic hypopituitarism or Kallmann's syndrome. Gonadotropin concentrations in four of five patients with constitutional delay of adolescence also were unaffected. In one boy with clinical and biochemical indices of late pubertal development, naloxone elicited a significant increase in LH levels in blood and urine, similar to the pattern observed in normal men. In contrast to results in experimental animals, naloxone did not suppress serum PRL concentration significantly in any subject. These observations suggest that: 1) endogenous opiate mechanisms are unlikely to constitute a principal factor in maintaining hypogonadotropism in idiopathic hypopituitarism, delayed adolescence, or Kallmann's syndrome, at least acutely; 2) endogenous opiate mechanisms also cannot be implicated in the acute regulation or PRL secretion in children; and 3) the capability of adult men, but not early pubertal boys, to respond with increased gonadotropin secretion during inhibition of opiate receptors suggests that maturation of the opiate-related neuroendocrine system occurs during the course of sexual development in the human.

Precocious and delayed puberty. Studies of FSH and LH production and metabolism

We measured the production rates and metabolic clearance, disappearance and excretion rates of FSH and LH as well as plasma testosterone and delta 4-androstenedione in males with precocious and delayed puberty. In precocious puberty, we found modestly elevated FSH production early in puberty, reaching adult levels by midpuberty and remaining constant thereafter. LH production was low early in puberty, reached high levels at midpuberty and then fell. The plasma testosterone concentrations paralleled the changes in LH. This suggests that moderate FSH production is achieved by early puberty and adult levels are reached by midpuberty. On the other hand LH production is low early in puberty, reaches high levels by midpuberty and then falls again towards the end of puberty. Constitutional delay in sexual development probably consists of several syndromes due either to a delay in LH production or to FSH production or to both. One patient with hypogonadotrophic hypogonadism was also studied. He showed relatively normal LH production but very low FSH production.