Growth hormone secretion in Turner's syndrome and influence of oxandrolone and ethinyl oestradiol

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.

Treatment of osteoporosis in children with glucocorticoid-treated diseases

Glucocorticoid induced osteoporosis (GIO) is the most frequent form of drug induced osteoporosis. Glucocorticoids affect osteoblastogenesis, osteoclastogenesis and promote the apoptosis of osteoblasts and osteocytes. A decrease of bone mineral density has been described in several pediatric diseases that require glucocorticoids, both as long-term replacement therapy, such as Congenital Adrenal Hyperplasia, and as treatment of acute phase or relapses, such as asthma, juvenile rheumatoid arthritis, inflammatory bowel diseases, systemic lupus erythematosus, organ transplantation and Steroid Sensitive Nephrotic Syndrome. The increasing number of children with GIO and at risk of fractures reflects the complex nature of this condition, and the need of development of anti-osteoporotic drugs. In this review, we focus on the mechanisms of GIO in some pediatric diseases and on treatment of osteoporosis. We also report data on new signaling pathways as potential targets for future anti-osteoporotic drugs.

Cardiovascular phenotype in Turner syndrome--integrating cardiology, genetics, and endocrinology

Cardiovascular disease is emerging as a cardinal trait of Turner syndrome, being responsible for half of the 3-fold excess mortality. Turner syndrome has been proposed as an independent risk marker for cardiovascular disease that manifests as congenital heart disease, aortic dilation and dissection, valvular heart disease, hypertension, thromboembolism, myocardial infarction, and stroke. Risk stratification is unfortunately not straightforward because risk markers derived from the general population inadequately identify the subset of females with Turner syndrome who will suffer events. A high prevalence of endocrine disorders adds to the complexity, exacerbating cardiovascular prognosis. Mounting knowledge about the prevalence and interplay of cardiovascular and endocrine disease in Turner syndrome is paralleled by improved understanding of the genetics of the X-chromosome in both normal health and disease. At present in Turner syndrome, this is most advanced for the SHOX gene, which partly explains the growth deficit. This review provides an up-to-date condensation of current state-of-the-art knowledge in Turner syndrome, the main focus being cardiovascular morbidity and mortality. The aim is to provide insight into pathogenesis of Turner syndrome with perspectives to advances in the understanding of genetics of the X-chromosome. The review also incorporates important endocrine features, in order to comprehensively explain the cardiovascular phenotype and to highlight how raised attention to endocrinology and genetics is important in the identification and modification of cardiovascular risk.

Efficacy and safety of oxandrolone in growth hormone-treated girls with turner syndrome

CONTEXT AND OBJECTIVE

GH therapy increases growth and adult height in Turner syndrome (TS). The benefit to risk ratio of adding the weak androgen oxandrolone (Ox) to GH is unclear.

DESIGN AND PARTICIPANTS

A randomized, placebo-controlled, double-blind, dose-response study was performed in 10 centers in The Netherlands. One hundred thirty-three patients with TS were included in age group 1 (2-7.99 yr), 2 (8-11.99 yr), or 3 (12-15.99 yr). Patients were treated with GH (1.33 mg/m(2) . d) from baseline, combined with placebo (Pl) or Ox in low (0.03 mg/kg . d) or conventional (0.06 mg/kg . d) dose from the age of 8 yr and estrogens from the age of 12 yr. Adult height gain (adult height minus predicted adult height) and safety parameters were systematically assessed.

RESULTS

Compared with GH+Pl, GH+Ox 0.03 increased adult height gain in the intention-to-treat analysis (mean +/- sd, 9.5 +/- 4.7 vs. 7.2 +/- 4.0 cm, P = 0.02) and per-protocol analysis (9.8 +/- 4.9 vs. 6.8 +/- 4.4 cm, P = 0.02). Partly due to accelerated bone maturation (P < 0.001), adult height gain on GH+Ox 0.06 was not significantly different from that on GH+Pl (8.3 +/- 4.7 vs. 7.2 +/- 4.0 cm, P = 0.3). Breast development was slower on GH+Ox (GH+Ox 0.03, P = 0.02; GH+Ox 0.06, P = 0.05), and more girls reported virilization on GH+Ox 0.06 than on GH+Pl (P < 0.001).

CONCLUSIONS

In GH-treated girls with TS, we discourage the use of the conventional Ox dosage (0.06 mg/kg . d) because of its low benefit to risk ratio. The addition of Ox 0.03 mg/kg . d modestly increases adult height gain and has a fairly good safety profile, except for some deceleration of breast development.

Growth hormone treatment of non-growth hormone-deficient growth disorders

Although a large body of data on efficacy and safety of growth hormone (GH) treatment for various non-growth hormone-deficient (GHD) growth disorders has accumulated from a combination of clinical trial and postmarketing sources in the last 20 years or more, there remain limitations. Clinical trial data have the advantage of direct comparison of well-matched, randomized patient groups receiving treatment (or not) under comparable conditions and, as such, provide the highest quality evidence of efficacy. Clinical trials, however, are typically too small for any statistically valid assessment for safety, which is more comprehensively addressed using postmarketing data. Consequently, while the efficacy of GH treatment in children with non-GHD growth disorders has been solidly established and, based on the combination of the rigor of the clinical trial data and numerical power of the postmarketing data, no major concerns exist regarding safety, additional long-term data are required.

Short-term growth hormone treatment in girls with Turner syndrome decreases fat mass and insulin sensitivity: a randomized, double-blind, placebo-controlled, crossover study

BACKGROUND

Most girls with Turner syndrome (TS) receive growth hormone (GH) treatment during childhood and adolescence, but controlled data on the effects on body composition and glucose metabolism are lacking.

OBJECTIVE

To study the effects of GH treatment on insulin sensitivity, glucose metabolism, bone turnover, and body composition.

METHODS

A randomized, placebo-controlled, crossover study was conducted with girls with TS. All girls with TS were treated with GH 0.1 IU/kg/d subcutaneously at bedtime or with placebo for 2 months and studied at the end of each period. Control subjects were studied once without treatment. Twelve girls with TS, aged 9.5 to 14.8 years (median: 12.9 years) and 16 age-matched control subjects (10.3-16.0 years; median: 12.1 years) were studied. Twenty-four-hour sampling of blood was performed; GH, insulin-like growth factor I (IGF-I), IGF binding proteins (IGFBPs), insulin, glucose, and lipolytic and gluconeogenic precursors were assayed, followed by an oral glucose tolerance test. Body composition was evaluated by dual-energy x-ray absorptiometry scanning and body mass index (BMI). Fasting bone markers were measured.

RESULTS

Height was reduced in TS as compared with control subjects. In the placebo situation, 24-hour integrated GH as well as IGF-I was significantly reduced in girls with TS compared with control subjects. Controlling for differences in lean body mass (LBM; or fat mass [FM]) and sexual development did not explain the difference in 24-hour integrated GH. Differences in sexual development, BMI, FM, insulin sensitivity, and IGFBP-3 could explain the difference in IGF-I between TS and control subjects. Carbohydrate metabolism in TS was comparable with control subjects. GH treatment induced insulin resistance, with increments in fasting glucose and insulin, as well as 24-hour insulin. Circulating levels of lipid and gluconeogenic substrates were comparable in TS and control subjects and unchanged in response to treatment. Bone markers increased in response to GH. Total FM was increased in girls with TS, accounted for by an increased FM in the arms and trunk, whereas LBM was decreased. Especially LBM in the legs was decreased. Overall, bone mineral content was diminished. Treatment with GH reduced FM in TS, especially in the arms and legs, and likewise increased total LBM, primarily in the trunk.

CONCLUSION

This study documented evidence of impaired GH secretion and action, disproportionate body composition, but a normal carbohydrate metabolism in girls with TS. Short-term GH administration was associated with favorable changes in body composition but also with relative impairment of glucose tolerance and insulin sensitivity. We recommend that glucose metabolism be monitored carefully during long-term GH treatment in these patients.

Turner syndrome and the heart: cardiovascular complications and treatment strategies

Turner syndrome is a condition usually associated with reduced final height, gonadal dysgenesis, and thus insufficient circulating levels of female sex steroids, and infertility. A number of other signs and symptoms are seen more frequently with the syndrome. With respect to cardiac function, congenital malformations of the heart and the great vessels, hypertension and ischemic heart disease, and increased risk of aortic dissection are all conditions that the pediatrician or the physician caring for females with Turner syndrome should keep in mind. Many girls and adolescents with Turner syndrome receive growth hormone (GH) treatment, which has so far been an effective and well-tolerated therapy. Nevertheless, because of the experience from acromegaly, the physician should monitor blood pressure and perform echocardiography, together with clinical examinations by a cardiologist at regular intervals. During adulthood most women with Turner syndrome are faced with premature menopause and the need for female hormone replacement therapy (HRT). During clinical evaluation of girls and women with Turner syndrome, these conditions and complications should be kept under surveillance. Here the cardiovascular complications of Turner syndrome are reviewed. The risk of congenital heart defects such as bicuspid aortic valves, aortic coarctation, other valve abnormalities, and septal defect is increased. Likewise, the risk of aortic dissection at a young age is increased, as is the risk of hypertension, ischemic heart disease, and stroke. GH therapy does not seem to adversely affect the heart, although longer-term follow-up studies are needed. In short-term studies, HRT lowers blood pressure, while any effect on the risk of ischemic heart disease has not been evaluated. Treatment with GH and HRT are discussed in relation to the heart and great vessels. Presently, the pathophysiology of the congenital cardiovascular malformation in Turner syndrome is unexplained, although different theories exist. Recommendations for clinical practice are given, including life-long surveillance of cardiac function, aortic diameter and blood pressure.

Aspects of the treatment of Turner syndrome

Several issues have to be considered when taking care of girls and women with Turner syndrome. During childhood, short stature is the primary concern and treatment with growth hormone (GH) is now widely used, often in conjunction with the androgen, oxandrolone. Recent studies indicate that doses used previously in the treatment of short stature have been too small. Induction of puberty should be performed at an appropriate age with reference to the peers of the patient. In adulthood, female sex hormone substitution should be offered to possibly prevent the increased morbidity seen in Turner syndrome, which consists of increased risk of fractures and osteoporosis, a clustering of diseases like ischaemic heart disease, hypertension, stroke and Type 2 diabetes, the latter entities being involved in the insulin resistance syndrome. Furthermore, hypothyreosis are often seen and the risk of Type 1 diabetes may also be increased. Congenital malformations of the heart are frequently seen in Turner syndrome, possibly increasing the risk of dissecting aorta aneurism. Liver enzymes are often elevated in Turner syndrome and there may be an increased risk of cirrhosis of the liver. Mortality does seem to be increased in Turner syndrome and women with the 'pure' 45,X karyotype do seem to be most severely affected. In the clinical practice of Turner syndrome, a careful monitoring of glucose and bone metabolism, weight, thyroid function and blood pressure should be performed. A cardiovascular risk profile should be determined and the patient informed concerning risks and benefits from sex hormone replacement therapy. Based on the available literature, sex hormone replacement therapy is highly recommended, although at present there are no longitudinal data documenting the long-term positive effect of sex steroid substitution. However, hypogonadism is expected to explain at least part of the decreased lifespan found in Turner syndrome. Since general physicians encounter Turner patients infrequently, it is recommended that the care and treatment of Turner syndrome is centralised.

Gonadal dysgenesis and bone metabolism

Gonadal dysgenesis is defined as congenital hypogonadism related to abnormalities of the sex chromosomes. Because sex steroids play a central role in the acquisition and maintenance of bone mass, studies have been done to investigate bone status in patients with gonadal dysgenesis, particularly Turner's syndrome and Klinefelter's syndrome, which are the two most common types. The severe estrogen deficiency characteristic of Turner's syndrome (44, X0) is associated with a significant bone mass decrease ascribable to increased bone turnover, as shown by histological studies and assays of bone turnover markers. Estrogen therapy is followed by a significant bone mass gain and a return to normal of bone turnover markers, suggesting that it is the estrogen deficiency rather than the chromosomal abnormality that causes the bone mass deficiency, although abnormalities in the renal metabolism of vitamin D have been reported. Combined therapy with estrogens and growth hormone seems beneficial during the prepubertal period. In Klinefelter's syndrome (47XXY), serum testosterone levels are at the lower end of the normal range and dihydrotestosterone levels are low. Histological studies show depressed osteoblast function and a decrease in 5-alpha-reductase activity responsible for partial tissue resistance to androgens. Assays of bone turnover markers show evidence of increased bone turnover. The bone deficiency is most marked at the femoral neck and seems correlated with serum testosterone and estradiol levels. Androgen therapy has favorable effects on the bone only if it is started before puberty. Recent data suggest that estrogens may contribute to the development of demineralization in KS and that bisphosphonate therapy may be beneficial.

Reduced free IGF-I and increased IGFBP-3 proteolysis in Turner syndrome: modulation by female sex steroids

The bioactivity of the growth hormone-insulin-like growth factor (IGF) system is reduced in Turner syndrome and may explain the reduction seen in final height. We compared levels of free and total IGF-I, immunoreactive and Western ligand blot IGF-binding protein (IGFBP)-3, and IGFBP-3 proteolysis in women with Turner syndrome (n = 23) before (T(B)) and during 6 mo treatment with 17beta-estradiol and norethisterone. An age-matched group of controls (n = 24) was included. Total IGF-I and immunoreactive levels of IGFBP-3 were comparable in T(B) and controls, whereas free IGF-I (P = 0.02) in T(B) was less than in controls. Western ligand blotting (WLB)-IGFBP-3 was significantly lower in T(B) than in controls (P = 0.0005). Accordingly, IGFBP-3 proteolysis was greater in Turner syndrome (P = 0.001). Female sex steroid treatment increased WLB-IGFBP-3 (P = 0.0005), whereas immunoreactive IGFBP-3 and IGFBP-3 proteolysis were normalized (P = 0.004). Free IGF-I remained unchanged (P = 0.8), with a tendency toward a decrease in total IGF-I (P = 0.1). In conclusion, despite normal total IGF-I and immunoreactive IGFBP-3, free serum IGF-I is less and IGFBP-3 proteolysis is greater in Turner syndrome than in controls. During sex steroid treatment, IGFBP-3 proteolysis normalized, without any change in free IGF-I.

Reduced androgen levels in adult turner syndrome: influence of female sex steroids and growth hormone status

BACKGROUND AND OBJECTIVES

In girls with Turner syndrome androgen levels are reduced. In order to assess androgen status in women with Turner syndrome, we compared untreated adult women with Turner syndrome with a group of normal women. In addition, the effects of female sex hormone replacement therapy and GH status on the levels of circulating androgens in Turner syndrome was examined.

DESIGN

All patients were receiving female hormone replacement therapy (HRT), which was discontinued four months prior to the initial examination. Patients were studied before and during HRT. Following the initial evaluation, patients were given cyclical HRT for six months consisting of either oral substitution (17beta-oestradiol with norethisterone from day 13-22), or transdermal oestrogen substitution (17beta-oestradiol) with 1 mg norethisterone administered orally from day 13-22. Control subjects were studied once in the early follicular stage of the menstrual cycle.

SUBJECTS

The study group consisted of 27 (33.2 +/- 7.9 years) patients with Turner syndrome and an age matched control group of 24 (32.7 +/- 7.6 years) normal women.

MEASUREMENTS

Body composition measures, SHBG, testosterone (T), free testosterone (FT), dihydrotestosterone (DHT), alpha-4-androstendione (A), dehydroepiandrosterone sulphate (DHEAS), 17beta-oestradiol (E2), oestrone (E1), oestrone sulphate (ES), 24 h integrated GH concentration (ICGH), insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein (IGFBP-3) were determined at baseline and after six months in women with Turner syndrome, and at baseline in control women.

RESULTS

Circulating levels of A, T, FT, DHT, and SHBG were reduced by 25-40% in comparison with age matched normal women. The level of DHEAS was normal. The level of E2 was undetectable and levels of E1 and ES were very low in untreated Turner women. Treatment with 17beta-oestradiol and norethisterone increased oestrogen to levels comparable to those of normal women, while further decreasing FT (P = 0.02), DHT (P = 0.04), and T (P = 0.1). In untreated women with Turner syndrome IGF-I correlated significantly with DHEAS (R = 0.503, P < 0.01), while in normal women IGF-I correlated with A (R = 0.637, P < 0.01), T (R = 0.536, P < 0.01), and FT (R = 0.700, P < 0.01). During hormonal replacement in women with Turner syndrome IGF-I correlated significantly with DHEAS (R = 0.547, P < 0.01). Employing multiple regression analysis IGFBP-3, ICGH, DHEAS and fat free mass explained 85% (adjusted R = 0.92, P < 0.0005) of the variation in the level of IGF-I in untreated Turner syndrome. In treated Turners IGFBP-3, ICGH, SHBG, T, and FT explained 78% (adjusted R = 0.88, P < 0.0005). In controls IGFBP-3, SHBG, BMI and age explained 74% (adjusted R = 0.86, P < 0.0005) of the variation in IGF-I, while GH status did not contribute at all.

CONCLUSION

The present study shows that many adults with Turner syndrome have reduced levels of circulating androgens, compared with an age-matched group of normal women. Conditions associated with Turner syndrome such as increased prevalence of sexual problems, reduced bone mineral content, osteoporosis, and an increased incidence of fractures and alterations in body composition could perhaps be alleviated or abolished by substitution with a low dose of androgens. Treatment with female hormonal replacement therapy is associated with a decrease in testosterone, free testosterone and dihydrotestosterone, possibly mediated by the androgenic effect of norethisterone. Furthermore significant differences in sex steroid levels, GH status and indices of body composition can be compatible with comparable levels of IGF-I in two very different groups of individuals.

Body composition and physical fitness are major determinants of the growth hormone-insulin-like growth factor axis aberrations in adult Turner's syndrome, with important modulations by treatment with 17 beta-estradiol

The objectives of this study were to 1) study the GH-insulin-like growth factor (IGF) axis in adult untreated Turner's syndrome compared to that in age-matched controls; 2) examine the effects of sex hormone substitution on this axis, 3) study the effects of route of administration of 17 beta-estradiol on the measured variables, and 4) examine the effects of sex steroids on hepatic function in Turner patients. Twenty-seven patients with Turner's syndrome were evaluated before and during sex hormone replacement, and an age-matched control group (n = 24) was evaluated once. Main outcome variables were GH and other measures of the GH-IGF axis, body composition, maximal oxygen uptake, sex hormone-binding globulin, and hepatic enzymes and proteins. The integrated 24-h GH concentration (IC-GH; micrograms per L/24 h) was reduced in women with Turner's syndrome (T) compared to controls [C; mean +/- SD, 18.3 +/- 12.0 (T) vs. 37.2 +/- 29.7 (C); P = 0.007]. However, multiple regression revealed that fat-free mass (FFM) and maximal oxygen uptake were significant explanatory variables (joint r = 0.77; P < 0.0005), accounting for 60% of the variance in the 24-h IC-GH. This association was also present in controls. After adjustment for these two variables, any difference in GH concentration between Turner patients and controls disappeared. Serum IGF-I and IGF-II were identical in Turner patients and controls despite the difference in 24-h IC-GH. The level of GH-binding protein (GHBP; nanomoles per L) was higher in Turner women [1.87 +/- 0.72 (T) vs. 1.22 +/- 0.33 (C); P = 0.0005]; after adjustment for FFM, the difference in GHBP levels disappeared between Turner patients and controls. During sex hormone treatment a significant increase was seen in the 24-h IC-GH (P = 0.02), FFM (percentage of weight; P < 0.0005) and maximal oxygen uptake (milliliters of O2 per kg/min; P = 0.02). Serum IGF-I was unchanged, whereas serum IGF-II (micrograms per L) decreased significantly [Turner, basal (TB), vs. Turner, treatment (TT), 860 +/- 135 vs. 823 +/- 150; P = 0.04]. Alanine aminotransferase (units per L), gamma-glutamyl transferase (units per L), and alkaline phosphatase (units per L) were significantly elevated during the basal study period, and all decreased during treatment [alanine amino-transferase, 55 +/- 55 (TB) vs. 30 +/- 20 (TT; P = 0.006); gamma-glutamyl transferase, 92 +/- 98 (TB) vs. 43 +/- 65 (TT; P = 0.003); alkaline phosphatase, 211 +/- 113 (TB) vs. 175 +/- 54 (TT); P = 0.06]. The route of administration of 17 beta-estradiol did not affect its actions. In conclusion, we found the GH-IGF axis in Turner's syndrome to be normal, with body composition and physical fitness exerting the same modifying effects on this axis as seen in the normal population. Sex hormone replacement in Turner's syndrome is associated with normalizing effects on the GH-IGF axis, body composition, physical fitness, and hepatic function. The lowering of hepatic enzymes is a surprising and hitherto undiscovered action of sex steroids. Finally, the route of administration of 17 beta-estradiol is of minor importance in Turner's syndrome.

Treatment of patients with Ullrich-Turner syndrome with conventional doses of growth hormone and the combination with testosterone or oxandrolone: effect on growth, IGF-I and IGFBP-3 concentrations

Thirty-nine girls with Ullrich-Turner syndrome (UTS) (median age 9.5 years) were treated with growth hormone (GH) with either 12 or 18 IU/m2 per week for 12 months followed by combination therapy with either oxandrolone (Ox) (0.0625 mg/kg/day po) or low-dose testosterone (T) (5 mg in every 2 weeks). Growth velocity improved significantly after 12 IU/m2 per week (6.4 +/- 1.7 cm/year vs 4.0 +/- 1.3 cm/year, x +/- SD, P < 0.001) and 18 IU/m2 per week of GH (6.5 +/- 1.3 cm/year vs 4.5 +/- 1.4 cm/year, P < 0.001). Ox, but not T was effective in maintaining growth velocity during the 2nd year of therapy (6.9 +/- 1.3 vs 5.3 +/- 1.5 cm/year). Basal insulin-like growth factor-I (IGF-I) concentrations were in the lower normal range and increased significantly in patients treated with 18 IU/m2 per week (357 +/- 180 ng/ml vs 160 +/- 84 ng/ml) and 12 IU/m2 per week (273 +/- 121 ng/ml vs 140 +/- 77 ng/ml). IGF-I concentrations increased further after addition of Ox (533 +/- 124 ng/ml, P < 0.001) or T (458 +/- 158, P < 0.05). IGFBP-3 concentrations were in the upper normal range before therapy and increased only moderately in both GH dosage groups. However, IGF binding protein-3 (IGFBP-3) concentrations were not affected by additional Ox or T treatment.

CONCLUSIONS

1. Conventional GH doses are effective in increasing growth velocity in UTS, especially, when combined with Ox.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of growth hormone administration frequency on 24-hour growth hormone profiles and levels of other growth related parameters in girls with Turner's syndrome. Dutch Working Group on Growth Hormone

OBJECTIVE

The optimal dose and frequency of GH administration in Turner's syndrome is unknown. There is some evidence that a schedule which mimics normal pulsatile GH secretion may be more effective than a single daily dose. We therefore wished to study the influence of the frequency of GH administration on 24-hour GH profiles and levels of other growth-related factors in Turner's syndrome.

DESIGN

Four weeks after initiation of 0.05 microgram/kg/day ethinyl oestradiol, we compared twice daily (b.i.d.-fractionated dose) with once daily (o.d.) s.c. injections of 6 IU GH/m2/day in a 2-week cross-over design with a 2-week washout interval. Each treatment period was concluded with 24-hour GH profile tests. Pretreatment plasma/serum levels of GH, IGF-I, binding proteins for GH (GHBP) and IGF-I (IGFBP-3) were used as a basis for comparison of the levels found after each regimen. A one-compartment open model was used for estimation of pharmacokinetic parameters.

SUBJECTS

Ten previously untreated girls with Turner's syndrome aged > or = 11 years.

MEASUREMENTS

Plasma levels of GHBP by standardized binding assay; GH, IGF-I, and IGFBP-3 serum/plasma levels by radioimmunoassay.

RESULTS

There were significantly higher maximum GH levels and a greater area under the curve with o.d. than with b.i.d. GH, while GH clearance was greater with b.i.d. The pharmacokinetic values with o.d. injections were in conformity with values for healthy and GH-deficient children. Pretreatment GHBP levels tended to be high compared with values in healthy prepubertal children. These levels decreased with GH therapy, significantly so with b.i.d. GH only. There was a significant increase in levels of IGF-I and IGFBP-3, irrespective of regimen. The IGF-I to IGFBP-3 ratio, a possible indicator of the growth response, rose significantly and comparably with both regimens. There was no consistent diurnal variation with either regimen in GHBP, IGF-I or IGFBP-3 levels. Four-hourly levels of GH, GHBP, IGF-I and IGFBP-3 were not correlated.

CONCLUSIONS

Although the 24-hour profiles differed during once or twice daily administration of the same total growth hormone dose, the diurnal pattern and mean levels of factors involved in the biological effects of GH are comparable for both regimens.

Conventional and nonconventional uses of growth hormone

Although GH has been available as a therapeutic agent for the GH-deficient child for more than 30 years, the conditions of its use have yet to be optimized. The availability of biosynthetic material has provided researchers with the opportunity to develop the protocols necessary to begin to finally answer the most fundamental questions pertaining to dose, frequency, and duration of treatment. It has also permitted the initiation of prospective trials in a large number of conditions that result in childhood short stature, with the expectation that some or many of them will be treated effectively and safely. Finally, it has opened the door to an entire spectrum of potentially new uses of GH and other growth factors for so-called nonconventional indications. That these have implications that range from the short-term rapid healing of a burn graft site, to the more efficient induction of ovulation, to the long-term preservation of lean body mass has excited the interest of investigators in many fields of medicine and physiology. Thus, the recent progress reported in this paper is really the beginning of the new research that will take place with GH and growth factors.

Effect of obesity on endogenous secretion of growth hormone in Turner's syndrome

Nocturnal growth hormone secretion over a 12 hour period was assessed at 20 minute intervals in 25 prepubertal subjects with Turner's syndrome and 11 normal prepubertal girls of short stature to try and elucidate the relationship between body weight and endogenous secretion of growth hormone in Turner's syndrome. There were no differences in mean growth hormone concentration, age, height, or growth velocity between the two groups. There was an age related decline in mean growth hormone concentration in patient's with Turner's syndrome in contrast to the age related increase in controls. Mean percentage of ideal body weight was significantly higher in the Turner's syndrome group than among controls and it increased with age. There was a strong inverse relationship between mean growth hormone concentration and percentage of ideal body weight in those with Turner's syndrome. Covariate analysis of the multiple linear regression of mean growth hormone concentration on age and percentage of ideal body weight in Turner's syndrome indicated that percentage of ideal body weight had a significant effect on endogenous secretion of growth hormone when age was held constant, but not the other way round. We conclude that the age related decline in endogenous secretion of growth hormone in Turner's syndrome is partly the result of increasing body weight with age. The significant influences of biological variables such as age and body weight in the interpretation of measurements of endogenous secretion of growth hormone in Turner's syndrome should be emphasised.

A distribution method for analysing the baseline of pulsatile endocrine signals as exemplified by 24-hour growth hormone profiles

OBJECTIVE

To develop a method for quantifying the distribution of concentrations present in hormone profiles, which would allow an observer-unbiased estimate of the time concentration attribute and to make an assessment of the baseline.

DESIGN

The log-transformed concentrations (regardless of their temporal attribute) are sorted and allocated to class intervals. The number of observations in each interval are then determined and expressed as a percentage of the total number of samples drawn in the study period. The data may be displayed as a frequency distribution or as a cumulative distribution. Cumulative distributions may be plotted as sigmoidal ogives or can be transformed into discrete probabilities (linear probits), which are then linear, and amenable to regression analysis. Probability analysis gives estimates of the mean (the value below which 50% of the observed concentrations lie, which we term 'OC50'). 'Baseline' can be defined in terms of percentage occupancy--the 'Observed Concentration for 5%' (which we term 'OC5') which is the threshold at or below which the hormone concentrations are measured 5% of the time.

PATIENTS

We report the use of applying this method to 24-hour growth hormone (GH) profiles from 63 children, 26 adults and one giant.

RESULTS

We demonstrate that GH effects (growth or gigantism) in these groups are more related to the baseline OC5 concentration than peak concentration (OC5 +/- 95% confidence limits: adults 0.05 +/- 0.04, peak-height-velocity pubertal 0.39 +/- 0.22, giant 8.9 mU/l).

CONCLUSIONS

Pulsatile hormone profiles can be analysed using this method in order to assess baseline and other concentration domains.

Skeletal size and bone mineral content in Turner's syndrome: relation to karyotype, estrogen treatment, physical fitness, and bone turnover

Bone mineral content (BMC), bone mineral density, and metacarpal dimensions were studied in 50 women with Turner's syndrome aged 21-45 years in relation to karyotype, estrogen treatment, physical fitness, and biochemical markers of bone turnover. No differences were found between the 25 women with karyotype 45.X and women with other karyotypes. Forty-six women had received estrogen. Significant partial correlations were found between bone mineral density of the forearm and duration of estrogen treatment and physical fitness. BMC of the lumbar spine corrected for vertebral height (BMC(C)spine) was directly correlated with duration of estrogen treatment and height, marginally correlated with physical fitness, and inversely correlated with age. Outer metacarpal width was positively correlated with duration of estrogen treatment, age at initiation of therapy, and body weight. The diameter of medullary space showed negative correlation with physical fitness and height, and positive correlation with age at initiation of estrogen treatment. Cortical thickness was positively correlated with duration of estrogen treatment, physical fitness, and height. No convincing effects of estrogen could be demonstrated in women below the age of 30. Above the age of 30, all bone mineral measurements were markedly elevated in women treated for longer than the average of this age group. BMC(C)spine was inversely correlated with biochemical markers of bone formation. Our results demonstrate that estrogen treatment and physical fitness are important determinants of bone mineral status in Turner's syndrome and add to the evidence that estrogen treatment increases BMC in Turner's syndrome.

Reproducibility of 24-hour serum growth hormone profiles in man

OBJECTIVE

To study the reproducibility of 24-h serum growth hormone (GH) concentration profiles in adults.

DESIGN

24-h serum GH concentrations were constructed by drawing blood samples at 20-min intervals. Four study occasions over a period of 1 year were chosen to assess the reproducibility.

SUBJECTS

Six healthy adult male volunteers of normal height and weight and aged between 20 and 22 years.

MEASURES

The resulting GH data arrays were analysed by Fourier transformation. Between and within individual variations were calculated and expressed in terms of coefficients of variation and data plotted to show variations between groups and individuals.

RESULTS

The frequency component of GH secretion occurred with a dominant periodicity of between 160 and 240 min. Precise estimates of spectral power (strength of oscillatory activity) and period were obtained for group data, but such estimates cannot be inferred from a single profile. There was no significant difference in 24-h mean serum GH concentration over the year of study: occasion 1 (February) mean 2.0 mU/l (SD 0.5); occasion 2 (March) mean 3.7 mU/l (SD 2.8); occasion 3 (July) mean 2.7 mU/l (SD 1.4); occasion 4 (February) 2.5 mU/l (SD 1.5) (mean within individual coefficient of variation 35%, range 9-58). The concentrations of factors known to influence GH synthesis and secretion, insulin-like growth factor I, thyroxine, testosterone and oestradiol, varied little over the year of study.

CONCLUSIONS

These data demonstrate that group data are reproducible in terms of oscillatory activity and the amount of GH secreted and that 24-h GH profiles should be used predominantly for analysing group data. The variability between individual profiles limits their value in the investigation of children with growth failure and suspected GH insufficiency.