Effect of low dose oxandrolone and testosterone treatment on the pituitary-testicular and GH axes in boys with constitutional delay of growth and puberty

A Shifting Relationship Between Sex Hormone-Binding Globulin and Total Testosterone Across Puberty in Boys

CONTEXT

Sex hormone-binding globulin (SHBG) is associated with levels of total testosterone (total-T), and both total-T and SHBG are associated with obesity.

OBJECTIVE

We aimed to clarify the nature of the relationship between testosterone and SHBG and improve our understanding of their relationships with obesity. We hypothesize that the hypothalamic-pituitary-gonadal axis contributes to the homeostasis of testosterone by increasing the production of gonadal testosterone through a feedback mechanism that might operate differently at different pubertal stages.

METHODS

We investigated the dynamics of the relationship between SHBG, total-T, and body mass index (BMI) throughout puberty (from age 9 to 17) using longitudinal data obtained in 507 males. The directionality of this relationship was explored using polygenic scores of SHBG and total-T, and a two-sample Mendelian Randomization (MR) in male adults.

RESULTS

Consistent with our hypothesis, we found positive relationships between SHBG and total-T at age 15 and 17 but either no relationship or a negative relationship during the earlier time points. Such shifting relationships explained age-related changes in the association between total-T and BMI. Polygenic scores of SHBG and total-T in mediation analyses and the two-sample MR in male adults suggested an effect of SHBG on total-T but also a somewhat weaker effect of total-T on SHBG. Two-sample MR also showed an effect of BMI on SHBG but no effect of SHBG on BMI.

CONCLUSION

These results clarify the nature of the relationship between testosterone and SHBG during puberty and adulthood and shed new light on their possible relationship with obesity.

Anti-Müllerian hormone and letrozole levels in boys with constitutional delay of growth and puberty treated with letrozole or testosterone

STUDY QUESTION

Does treatment of constitutional delay of growth and puberty (CDGP) in boys with aromatase inhibitor letrozole (Lz) or conventional low-dose testosterone (T) have differing effects on developing seminiferous epithelium?

SUMMARY ANSWER

Anti-Müllerian hormone (AMH) declined similarly in both treatment groups, and the two Sertoli cell-derived markers (AMH and inhibin B (iB)) exhibited differing responses to changes in gonadotrophin milieu.

WHAT IS KNOWN ALREADY

Boys with CDGP may benefit from puberty-inducing medication. Peroral Lz activates gonadotrophin secretion, whereas intramuscular low-dose T may transiently suppress gonadotrophins and iB.

STUDY DESIGN, SIZE, DURATION

Sera of 28 boys with CDGP who participated in a randomised, controlled, open-label trial at four paediatric centres in Finland between August 2013 and January 2017 were analysed. The patients were randomly assigned to receive either Lz (2.5 mg/day) (n = 15) or T (1 mg/kg/month) (n = 13) for 6 months.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The 28 patients were at least 14 years of age, showed first signs of puberty, wanted medical attention for CDGP and were evaluated at 0, 3, 6 and 12 months of visits. AMH levels were measured with an electrochemiluminescence immunoassay and Lz levels with liquid chromatography coupled with tandem mass spectrometry.

MAIN RESULTS AND THE ROLE OF CHANCE

AMH levels decreased in both treatment groups during the 12-month follow-up (P < 0.0001). Between 0 and 3 months, the changes in gonadotrophin levels (increase in the Lz group, decrease in the T group) correlated strongly with the changes in levels of iB (FSH vs iB, r = 0.55, P = 0.002; LH vs iB, r = 0.72, P < 0.0001), but not with the changes in AMH (P = NS). At 12 months, AMH levels did not differ between the groups (P = NS). Serum Lz levels (range, 124-1262 nmol/L) were largely explained by the Lz dose per weight (at 3 months r = 0.62, P = 0.01; at 6 months r = 0.52, P = 0.05). Lz levels did not associate with changes in indices of hypothalamic-pituitary-gonadal axis activity or Sertoli cell markers (in all, P = NS).

LIMITATIONS, REASONS FOR CAUTION

The original trial was not blinded for practical reasons and included a limited number of participants.

WIDER IMPLICATIONS OF THE FINDINGS

In early puberty, treatment-induced gonadotrophin stimulus was unable to counteract the androgen-mediated decrease in AMH, while changes in iB levels were associated with changes in gonadotrophin levels. AMH decreased similarly in both groups during the treatment, reassuring safety of developing seminiferous epithelium in both treatment approaches. Since a fixed dose of Lz induced variable serum Lz levels with a desired puberty-promoting effect in all boys, more research is needed to aim at a minimal efficient dose per weight.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Academy of Finland, the Foundation for Pediatric Research, the Emil Aaltonen Foundation, Sigrid Juselius Foundation and Helsinki University Hospital Research Funds. The authors have nothing to disclose.

TRIAL REGISTRATION NUMBER

NCT01797718.

Testosterone Therapy in Adolescent Boys: The Need for a Structured Approach

BACKGROUND

In adolescents, testosterone may have several effects including promotion of secondary sexual characteristics and pubertal growth, attainment of optimal muscle mass and peak bone mass, optimization of the metabolic profile, and psychosocial maturation and well-being.

SUMMARY

Testosterone therapy is a cornerstone of the management of hypogonadism in boys. Since the initial report of the chemical synthesis of testosterone, several formulations have continued to develop, and although many of these have been used in boys, none of them have been studied in detail in this age group. Given the wide ranging effects of testosterone, the level of evidence for their effects in boys and the heterogeneity of conditions that lead to early-onset hypogonadism, a standardized protocol for monitoring testosterone replacement in this age group is needed. Key Messages: In this review, we focus on the perceived benefits of androgen replacement in boys affected by pubertal delay and highlight the need to improve the health monitoring of boys who receive androgen replacement therapy, proposing different approaches based on the underlying pathophysiology.

Letrozole versus testosterone for promotion of endogenous puberty in boys with constitutional delay of growth and puberty: a randomised controlled phase 3 trial

BACKGROUND

The treatment of constitutional delay of growth and puberty (CDGP) is an underinvestigated area in adolescent medicine. We tested the hypothesis that peroral aromatase inhibition with letrozole is more efficacious than intramuscular injection of low-dose testosterone in inducing puberty in boys with CDGP.

METHODS

We did a randomised, controlled, open-label trial at four paediatric centres in Finland. Boys aged at least 14 years with CDGP who wanted medical intervention and exhibited the first signs of puberty were randomly assigned in blocks of ten to receive either six intramuscular injections of low-dose testosterone (about 1 mg/kg bodyweight) every 4 weeks for 6 months or peroral letrozole 2·5 mg once daily for 6 months. All boys were followed up for 6 months after the end of treatment. The primary outcomes were changes in testicular volume and hormonal markers of puberty at 6 months after treatment initiation, which were assessed in all participants who received the assigned treatment. All patients were included in the safety analysis. This study is registered with ClinicalTrials.gov, number NCT01797718.

FINDINGS

Between Aug 1, 2013, and Jan 30, 2017, 30 boys were randomly assigned to receive testosterone (n=15) or letrozole (n=15). One boy in the testosterone group was excluded from the primary analyses because of a protocol deviation. During treatment, boys in the letrozole group had higher serum concentrations of luteinising hormone, follicle-stimulating hormone, testosterone, and inhibin B than did boys in the testosterone group. Testicular growth from baseline to 6 months was greater in the letrozole group than in the testosterone group (7·2 mL [95% CI 5·2-9·3] vs 2·2 mL [1·4-2·9]; between-group difference per month 0·9 mL [95% CI 0·6-1·2], p<0·0001). Most adverse events were mild. One boy in the testosterone group had aggressive behaviour for 1 week after each injection, and one boy in the letrozole group had increased irritability at 6 months.

INTERPRETATION

Letrozole might be a feasible alternative treatment to low-dose testosterone for boys with CDGP who opt for medical intervention. However, the risks and benefits of manipulating the reproductive axis during early puberty should be weighed carefully.

FUNDING

Helsinki University Hospital, Academy of Finland, and Finnish Foundation for Pediatric Research.

Oxandrolone Treatment Results in an Increased Risk of Gonadarche in Prepubertal Boys With Klinefelter Syndrome

CONTEXT

Klinefelter syndrome (KS) is a common genetic condition in which males have an extra X chromosome. KS is associated with testosterone deficiency, neurodevelopmental delays, and cardiometabolic disorders. There has been recent interest in prepubertal androgen treatment; however, the effects on puberty and gonadal function are unknown.

OBJECTIVE

To compare onset of puberty and testicular function in prepubertal boys treated with 2 years of oxandrolone (Ox) vs placebo (Pl).

DESIGN

Double-blind, randomized, controlled trial.

SETTING

Single tertiary care referral center.

PARTICIPANTS

Eighty prepubertal boys with KS; mean age: 8.0 ± 2.2 years (range: 4 to 12).

INTERVENTIONS

Ox 0.05 mg/kg vs identical-appearing Pl capsule given for 2 years.

OUTCOME MEASURES

Onset of gonadarche (testicular volume ≥4 mL) and onset of pubarche (Tanner 2 pubic hair); change in testicular hormone concentrations.

RESULTS

Ox-treated group had 20.5 times higher odds of reaching gonadarche (OR 95% CI: 6.5, 77.8) and 28.1 times higher odds of reaching pubarche (OR 95% CI: 8.8, 110.4) during the 2-year study period after adjusting for baseline age. Gonadarche and pubarche both occurred at a younger age in the Ox group (gonadarche: 9.8 ± 1.5 vs 12.1 ± 1.0 years, P < 0.001; pubarche: 10.2 ± 1.1 vs 11.6 ± 1.3 years, P = 0.02). Serum concentrations of testicular hormones and gonadotropins were not different between groups.

CONCLUSIONS

Two years of Ox treatment in prepubertal boys with KS results in an increased risk of early gonadarche, on average 2 years earlier than in Pl-treated boys. Ox did not affect serum concentrations of testicular hormones.

Diagnostic utility of testosterone priming prior to dynamic tests to differentiate constitutional delay in puberty from isolated hypogonadotropic hypogonadism

CONTEXT

Differentiation between constitutional delay in puberty (CDP) and isolated hypogonadotropic hypogonadism (IHH) during adolescence is a great clinical challenge, and the available diagnostic tests are of limited value.

OBJECTIVE

To study the effect of withdrawal of short-term, low-dose testosterone therapy (testosterone priming) on the discriminatory power of dynamic tests for hypothalamo-pituitary-testicular axis to differentiate CDP from IHH.

DESIGN

A prospective study (n = 30) consisting of 20 boys with delayed puberty (group A) and 10 patients with IHH (group B).

INTERVENTION

Patients in groups A and B underwent Triptorelin and hCG stimulation tests, prior to and 2 months after withdrawal of 'testosterone priming' (100 mg intramuscularly 4 weekly for 3 months) and were followed up until the onset of puberty or 18 years of age, whichever was earlier.

RESULTS

At baseline, Triptorelin-stimulated 4 h LH, with a cut-off of 2·8 IU/l, and hCG-stimulated day 7 testosterone with a cut-off of 3·8 nmol/l had sensitivities of 80% each, and specificities of 93% and 87%, respectively, to diagnose CDP. After withdrawal of testosterone, a 4 h LH cut-off of 14·7 IU/l and day 7 testosterone cut-off of 10·3 nmol/l had sensitivities of 93% and 88% respectively, and specificity and positive predictive value of 100% each. A basal inhibin B > 94·7 ng/l was discriminatory for diagnosing CDP after withdrawal of testosterone priming.

CONCLUSIONS

Inhibin B levels or 4 h LH after Triptorelin stimulation are the best discriminatory tests to differentiate CDP from IHH, when performed after withdrawal of 'testosterone priming'.

Estrogens and Androgens in Skeletal Physiology and Pathophysiology

Estrogens and androgens influence the growth and maintenance of the mammalian skeleton and are responsible for its sexual dimorphism. Estrogen deficiency at menopause or loss of both estrogens and androgens in elderly men contribute to the development of osteoporosis, one of the most common and impactful metabolic diseases of old age. In the last 20 years, basic and clinical research advances, genetic insights from humans and rodents, and newer imaging technologies have changed considerably the landscape of our understanding of bone biology as well as the relationship between sex steroids and the physiology and pathophysiology of bone metabolism. Together with the appreciation of the side effects of estrogen-related therapies on breast cancer and cardiovascular diseases, these advances have also drastically altered the treatment of osteoporosis. In this article, we provide a comprehensive review of the molecular and cellular mechanisms of action of estrogens and androgens on bone, their influences on skeletal homeostasis during growth and adulthood, the pathogenetic mechanisms of the adverse effects of their deficiency on the female and male skeleton, as well as the role of natural and synthetic estrogenic or androgenic compounds in the pharmacotherapy of osteoporosis. We highlight latest advances on the crosstalk between hormonal and mechanical signals, the relevance of the antioxidant properties of estrogens and androgens, the difference of their cellular targets in different bone envelopes, the role of estrogen deficiency in male osteoporosis, and the contribution of estrogen or androgen deficiency to the monomorphic effects of aging on skeletal involution.

The investigation of children and adolescents with abnormalities of pubertal timing

Concerns with pubertal development are common and can cause considerable distress to patients and their carers. Many presentations reflect normal variations of pubertal timing and primarily require reassurance, although patients may opt for interventions. Other presentations need active management to avoid significant adverse effects on growth and psychosocial development. All should undergo careful assessment, particularly as some children or adolescents presenting with abnormalities in pubertal timing may have serious pathology which requires urgent investigations and treatment. This review describes the appropriate investigations and their interpretation for young people presenting with disorders in pubertal timing.

A Novel Drug-Mouse Phenotypic Similarity Method Detects Molecular Determinants of Drug Effects

The molecular mechanisms that translate drug treatment into beneficial and unwanted effects are largely unknown. We present here a novel approach to detect gene-drug and gene-side effect associations based on the phenotypic similarity of drugs and single gene perturbations in mice that account for the polypharmacological property of drugs. We scored the phenotypic similarity of human side effect profiles of 1,667 small molecules and biologicals to profiles of phenotypic traits of 5,384 mouse genes. The benchmarking with known relationships revealed a strong enrichment of physical and indirect drug-target connections, causative drug target-side effect links as well as gene-drug links involved in pharmacogenetic associations among phenotypically similar gene-drug pairs. The validation by in vitro assays and the experimental verification of an unknown connection between oxandrolone and prokineticin receptor 2 reinforces the ability of this method to provide new molecular insights underlying drug treatment. Thus, this approach may aid in the proposal of novel and personalized treatments.

In order to avoid unwanted effects of current drug interventions, it is necessary to expand the knowledge of the molecular mechanisms related to drug action. Side effects offer insight into drug action, as for example similar side effects of unrelated drugs can be caused by their common off-targets. Moreover, the phenotypes of systematic single gene perturbation screenings in mice strongly contribute to the comprehension of gene function. Here, we present a novel approach that detects molecular interactions of drugs based on the phenotypic similarity of drugs and mouse models. The method is benchmarked with diverse data sets including drug-target interactions as well as gene-drug links of pharmacogenetic associations and validated by in vitro assays.

Effect of oxandrolone and timing of oral ethinylestradiol initiation on pubertal progression, height velocity and bone maturation in the UK Turner study

BACKGROUND

A UK study showed final height in Turner syndrome (TS) girls receiving growth hormone is affected by age at pubertal induction and oxandrolone (Ox). Using data from that study, we analysed the effect of timing of oral ethinylestradiol (EE2) and Ox on height velocity (HV), bone maturation and pubertal progression, and compared growth response in EE2-treated versus spontaneous puberty.

METHODS

Analysis of HV, bone age and pubertal stage in 92 TS girls (7-13 years) randomised to Ox (0.05 mg/kg/day; max: 2.5 mg/day) or placebo from 9 years, and EE2 (year 1: 2 µg/day; year 2: 4 µg/day; year 3: 6/8/10 µg/day×4 months) or placebo at 12 years with EE2 at 14 years. Girls enrolled at >12.25 years received EE2 at 14 years ('late group').

RESULTS

Fifty-six girls were randomised to EE2 at 12 years (n=28, 11 Ox) or 14 years (n=28, 13 Ox); there were 19 girls in the late group (9 Ox) and 17 girls with spontaneous puberty (10 Ox). Girls receiving EE2 at 12 versus 14 years had faster bone maturation, but neither group showed acceleration. Ox increased HV without altering bone maturation or pubertal progression. Girls with spontaneous puberty had greater pubertal growth (mean PHV 8.5 cm/year; p<0.001) and height gain (p<0.001) than EE2-treated girls despite similar mean enrolment height SD and dysmorphology scores.

CONCLUSION

Pubertal induction with EE2 does not replicate the acceleration observed in unaffected girls or TS girls with spontaneous puberty.

Pubertal growth and serum testosterone and estradiol levels in boys

BACKGROUND/AIMS

To study serum testosterone and estradiol in healthy boys in relation to growth during puberty up to peak height velocity (PHV).

METHODS

Growth velocity was analyzed through testosterone (n = 41) and 17β-estradiol (n = 37) 24-hour profiles in a dose-response model. Participants were 26 healthy boys admitted for short or tall stature or participating as healthy volunteers at the Queen Silvia Children's Hospital. Other inclusion criteria included the following: gestational age 37-42 weeks, birth weight and length >-2 standard deviation score (SDS) and prepubertal height and weight within ± 3 SDS. Testosterone was measured using a modified radioimmunoassay (RIA) with a detection limit of 0.03 nmol/l. Estradiol was determined using an ultrasensitive extraction RIA with a detection limit 4 pmol/l. A sixth-grade polynomial was fitted to each child's growth data, giving growth velocity and age at PHV.

RESULTS

Growth velocity increased by 50% from prepubertal growth to PHV at a morning testosterone level of 3.1 nmol/l (95% confidence interval 2.4-4.2), EC50. The corresponding EC50 of 17β-estradiol was 6.5 pmol/l (3.2-13). Boys approaching PHV (<4% remaining) had morning testosterone levels >10 nmol/l and 17β-estradiol >9 pmol/l.

CONCLUSION

Observed early puberty/initial mid puberty morning testosterone levels of 2.4-4.2 nmol/l are associated with a 50% increase in growth velocity from prepubertal growth to PHV in healthy boys.

Effects of three different medications on metabolic parameters and testicular volume in patients with hypogonadotropic hypogonadism: 3-year experience

INTRODUCTION

The aim of this study was to demonstrate the influences of three different treatment strategies on biochemical parameters and testicular volume (TV) in patients with idiopathic hypogonadotropic hypogonadism (IHH).

SUBJECTS DESIGN AND METHODS

Seventy-seven never-treated patients with IHH and age and body mass index (BMI)-matched 42 healthy controls were analysed in a retrospective design. Twenty-eight patients were treated with testosterone esters (TE), 25 patients were treated with human chorionic gonadotropin (hCG) and 24 patients were treated with testosterone gel (TG). Biochemical parameters, tanner stages (TS) and TV were evaluated before and after 6 months of treatment.

RESULTS

Pretreatment TV, TS and biochemical test results were similar among the three treatment subgroup. In the TE-treated group, BMI, haemoglobin, haematocrit, creatinine, triglyceride, total testosterone (TT), TS and TV increased, but HDL-cholesterol (C) and urea level decreased significantly. In the hCG-treated group, triglyceride level decreased, and luteinizing hormone level, TS and TV increased significantly. BMI, TT, TS and TV increased, and leucocyte count, total-C, HDL-C levels decreased significantly in the TG-treated patients. No treatment type resulted in any changes in insulin resistance markers.

CONCLUSION

hCG treatment resulted in favourable effects particularly on TV and lipid parameters. When TV improvement is considered less important, TG treatment may be a better option for older patients with IHH because of its easy use, neutral effects on triglyceride, haemoglobin and haematocrit, and its beneficial effects on total cholesterol level.

An approach to constitutional delay of growth and puberty

Constitutional delay of growth and puberty is a transient state of hypogonadotropic hypogonadism associated with prolongation of childhood phase of growth, delayed skeletal maturation, delayed and attenuated pubertal growth spurt, and relatively low insulin-like growth factor-1 secretion. In a considerable number of cases, the final adult height (Ht) does not reach the mid-parental or the predicted adult Ht for the individual, with some degree of disproportionately short trunk. In the pre-pubertal male, testosterone (T) replacement therapy can be used to induce pubertal development, accelerate growth and relieve the psychosocial complaints of the adolescents. However, some issues in the management are still unresolved. These include type, optimal timing, dose and duration of sex steroid treatment and the possible use of adjunctive or alternate therapy including: oxandrolone, aromatase inhibitors and human growth hormone.

Androgen therapy for delayed male puberty

PURPOSE OF REVIEW

Delayed puberty in men is a commonly presenting problem to paediatricians and an understanding of the available evidence on cause, treatments and outcomes is important to guide practice.

RECENT FINDINGS

Understanding of the regulation of the onset of puberty is gradually unfolding, although the genetic factors that dictate the timing of puberty in individuals and families remain poorly elucidated. Mutations and polymorphisms in candidate genes are being actively studied and it is likely that there is significant overlap between traditional diagnostic categories. Also, environmental endocrine disruptors may interact with the genetic regulation of puberty. Delayed puberty may not always be a benign condition, with increased risks of failing to achieve target height, adverse psychological and educational consequences, delayed sexual and psychosocial integration into society and effects on skeletal proportions and bone mass reported. Appropriate evaluation and follow-up is needed to guide clinical practice, particularly to distinguish constitutional delay in growth and puberty from that associated with other medical disease or permanent disorders.

SUMMARY

In milder cases of delayed puberty, treatment is often not required; however, considerable evidence exists for the efficacy and safety of short courses of low-dose testosterone therapy for appropriately selected individuals. This treatment is associated with high levels of patient satisfaction. There is not yet sufficient evidence for the routine use of other therapies (e.g. growth hormone, aromatase inhibitors) for constitutional delay in growth and puberty and better characterization of cause may lead to more targeted individual therapy.

The role of sex steroids in controlling pubertal growth

Longitudinal growth, which is primarily due to chondrocytic activity at the level of the epiphyseal growth plate, is influenced by many hormones and growth factors in an endocrine and paracrine manner. Their influence is even more complex during the accelerated growth period of puberty that accounts for about 20% of final adult height. Although abnormalities of growth during puberty are very common, the underlying mechanisms that govern the beginning and cessation of pubertal growth at the level of the growth plate are poorly understood. Sex steroids play a crucial role in pubertal growth both at the systemic level via the GH/IGF-1 axis and at the local level of the epiphyseal growth plate. In both sexes it is now accepted that oestrogen is the critical hormone in controlling growth plate acceleration and fusion. This paper reviews the mechanisms that influence pubertal growth and the problems that are associated with disorders of gonadal function.

Feedback regulation of growth hormone synthesis and secretion in fish and the emerging concept of intrapituitary feedback loop

Growth hormone (GH) is known to play a key role in the regulation of body growth and metabolism. Similar to mammals, GH secretion in fish is under the control of hypothalamic factors. Besides, signals generated within the pituitary and/or from peripheral tissues/organs can also exert a feedback control on GH release by effects acting on both the hypothalamus and/or anterior pituitary. Among these feedback signals, the functional role of IGF is well conserved from fish to mammals. In contrast, the effects of steroids and thyroid hormones are more variable and appear to be species-specific. Recently, a novel intrapituitary feedback loop regulating GH release and GH gene expression has been identified in fish. This feedback loop has three functional components: (i) LH induction of GH release from somatotrophs, (ii) amplification of GH secretion by GH autoregulation in somatotrophs, and (iii) GH feedback inhibition of LH release from neighboring gonadotrophs. In this article, the mechanisms for feedback control of GH synthesis and secretion are reviewed and functional implications of this local feedback loop are discussed. This intrapituitary feedback loop may represent a new facet of pituitary research with potential applications in aquaculture and clinical studies.

New facets of androgen replacement therapy during childhood and adolescence

The goals of androgen therapy for adolescents are to promote linear growth and secondary sexual characteristics, at the same time as permitting the normal accrual of muscle mass and bone mineral content. Secondary goals are mainly in the psychosocial sphere, in which pubertally delayed boys feel that they look too young, are not considered a 'peer' in their age group and have difficulty competing in athletic endeavours. These goals are irrespective of the causes of delayed pubertal development: constitutional delay of growth and puberty (CDGP), a transient but very common form of pubertal delay and, much less commonly, primary or secondary permanent hypogonadism. Not all boys with CDGP require testosterone therapy, but those that come to a referral practice are likely candidates, as the watchful waiting period has finished. Although a range of androgen preparations is available for adults (injectable, oral, implantable and cutaneous patches and gels), most are drug delivery devices that are appropriate for full adult androgen replacement. These doses are too large for the induction of puberty. Therefore, at present, the injectable form is the only one that is easily adaptable for the increasing amounts of androgen necessary for the various stages of pubertal development. All preparations deliver testosterone that is readily converted to dihydrotestosterone by 5-alpha reductase. The author's practice is to begin with injecting 50-75 mg of one of the long-acting esters (enanthate or cypionate) per month, and gradually escalate to 100-150 mg/month, before changing to twice monthly dosage. As most adolescents have delayed puberty, the therapy is needed for 6-18 months before the hypothalamic-pituitary-gonadal axis functions at the late adolescent/adult level in those with CDGP. Those with permanent hypogonadism will require lifelong therapy. Once adequate virilisation is induced, and virtually full adult height is reached, any of the therapies noted above can be used in those permanently hypogonadal, whether primarily or secondarily.

Testosterone inhibition of growth hormone release stimulated by a growth hormone secretagogue: studies in the rat and dog

Anabolic steroids are frequently taken by athletes and bodybuilders together with recombinant human GH (rhGH), though there is some scientific evidence that the use of anabolic steroids reverses the rhGH-induced effects. Recently, we have shown that treatment with rhGH (0.2 IU/kg s.c., daily x 12 days) in the dog markedly reduced the canine GH (cGH) responses stimulated by EP51216, a GH secretagogue (GHS), evaluated after 3 and 5 daily rhGH injections, and that the inhibition was still present a few days after rhGH discontinuation. The aim of the present study was to evaluate in the dog the GH response to EP51216 (125 mug/kg i.v.) in a condition of enhanced androgenic function (i.e. acute injection or 15-day treatment with testosterone at the dose of 2 mg/kg i.m. on alternate days), and in the hypophysectomized rat the hypothalamic and hippocampal expression of ghrelin, the receptor of GHSs (GHS-R), GH-releasing hormone (GHRH) and somatostatin (SS) after specific hormonal replacement therapies (testosterone, 1 mg/kg/day s.c.; hydrocortisone, 500 mug/kg/day s.c.; rhGH, 400 mug/kg/day s.c.; 0.9% saline 0.1 ml/kg/day s.c.; x11 days). In the dog experiments, under baseline conditions, a single injection of EP51216 elicited an abrupt rise of plasma cGH. Twenty-four hours from the acute bolus injection of testosterone, C(max) and AUC(0-90) of the GHS-stimulated cGH response were significantly lower than baseline cGH response; 5 days later, there was still a significant decrease of either parameter versus the original values. Short-term treatment with testosterone markedly reduced the GHS-stimulated cGH responses evaluated during (5th bolus) and at the end (8th bolus) of testosterone treatment. Four and 8 days after testosterone withdrawal, the EP51216-stimulated cGH response was still significantly reduced when compared with that under baseline conditions. Plasma concentrations of insulin-like growth factor 1 (IGF-1) were stable until the 5th bolus of testosterone and decreased progressively in the remaining time of the testosterone treatment; 4 and 8 days from treatment withdrawal, IGF-1 levels were still suppressed. In rat studies, hypothalamic mRNA levels of GHS-R were significantly reduced by treatments with testosterone and hydrocortisone, whereas hippocampal expressions of ghrelin, GHRH and SS were reduced by rhGH replacement therapy. In conclusion, these studies show that a single administration of testosterone can abrogate the cGH response ensuing acute stimulation by a GHS; the inhibitory effect of testosterone on the cGH response to GHS is present during and even 8 days after termination of a short-lived treatment with testosterone; these events occur via a

Ethinylestradiol and testosterone have divergent effects on circulating IGF system components in adolescents with constitutional tall stature

OBJECTIVE

Pharmacological doses of estrogens or testosterone are used to limit the final height of girls or boys with constitutional tall stature but the mechanism behind this growth inhibition is still debated. We therefore studied the changes in the circulating components of the insulin-like growth factor (IGF) system during high dose sex steroid therapy.

DESIGN AND METHODS

Twenty three girls and twenty boys with constitutional tall stature were treated with 100 microg ethinylestradiol per day or 250 mg testosterone ester every 14 days respectively. In 19 girls and 18 boys, the levels of IGF-I, free IGF-I, IGF-II, acid-labile subunit (ALS) and IGF binding proteins (IGFBP)-2 to -6 were measured before and 3-6 months after the start of therapy (group 1). In 18 girls and 11 boys, samples were collected at the end of therapy and 3 to 6 months afterwards (group 2). Fourteen girls and nine boys belonged to both groups. All parameters were measured by radioimmunoassay or ELISA.

RESULTS

Levels of IGF-I were decreased significantly by estrogen treatment but remained unchanged during testosterone treatment. Free IGF-I decreased during estrogen treatment but increased during testosterone therapy. Estrogens increased IGF-II and testosterone reduced it. The important reduction of IGFBP-2 during estrogen therapy is not reproduced by androgen therapy, neither is the stimulation by estrogens of IGFBP-4. IGFBP-3 is not modulated by either sex steroid. We found that IGFBP-6 is up-regulated by testosterone but not by estrogens; the reverse is true for ALS, which increased during estrogen treatment but remained unchanged during testosterone treatment.

CONCLUSIONS

Our findings demonstrate that androgens and estrogens exert differential effects on the circulating levels of several IGF components.