Adrenarche in Prader-Willi syndrome appears not related to insulin sensitivity and serum adiponectin

Prader-Willi syndrome (PWS) is a genetic disorder characterized by dysmorphic features, obesity, hypogonadism, hypotonia and mental retardation. Obesity has been linked to insulin resistance and the latter has also been associated with premature adrenarche. Since up to date a controlled study to investigate adrenarche and its hormonal regulation was lacking in PWS, our aim was to assess whether prepubertal PWS patients develop premature adrenarche and its relationship with markers of insulin sensitivity. Fourteen prepubertal children with PWS (6 M, 8 F) and 10 non-syndromal simple obese matched controls (5 M, 5 F) participated (mean age: 7.62 +/- 1.84 years). A fasting blood sample was obtained for adrenal and ovarian androgens, sex hormone binding globulin, insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-1, leptin, adiponectin and a lipid profile. Thereafter an oral glucose tolerance test was performed. PWS patients were smaller at birth and a higher proportion displayed premature pubarche. No differences were found in testosterone, androstenedione, sex hormone binding globulin, free androgen index, homeostatic model assessment-IR, 2-hour insulin, leptin or adiponectin levels. 17-hydroxyprogesterone and DHEAS levels however, were significantly higher in PWS. IGF-I levels were significantly lower in PWS and correlated significantly with height SDS (p < 0.05). In conclusion, a higher proportion of premature adrenarche in our PW patients was observed, which was not explained by differences in insulin sensitivity or plasma levels of adipokines and IGF-I.     

Adrenal androgens in obese boys before and after weight loss

The adrenal steroid secretion was studied in 6 prepubertal obese boys and 6 obese boys at the first stage of sexual maturation according to Tanner. Twelve normal boys, closely matched for age and stage of sexual maturation, were also studied as controls. Pregnenolone and dehydroepiandrosterone plasma levels were found to be significantly (P less than 0.001) higher in both groups when compared with normal boys. All the values, apart from pregnenolone in the prepubertal group, returned to normal after weight loss. Progesterone was found significantly increased (P less than 0.001) in both groups and normal after weight loss. 17-OH-progesterone plasma levels showed no significant difference between the obese and control groups. Androstenedione was increased in the prepubertal group before and normal after weight loss; no significant difference was found in the other group. Testosterone and estradiol showed normal values in the two groups both before and after weight loss. Cortisol showed a similar pattern. It can be concluded that an increased cortico-adrenal activity is present in obese boys as already reported in obese girls. This finding could explain the precocious adrenarche which often occurs in these patients. The increased adrenal androgen secretion might be due to an increased cortico adrenal stimulating hormone secretion or to an enhanced adrenal sensitivity to this hypothetical hormone.     

A child with pituitary gigantism and precocious adrenarche: does GH and/or PRL advance the onset of adrenarche?

We describe a female child with pituitary gigantism and precocious adrenarche. From two years of age she showed unusual overgrowth, and at 5 years old she was 133.5 cm (+ 5.5 SD) tall and weighed 40.5 kg. Her precocious manifestations were public hair, acne vulgaris, hirsutism, and advanced bone age. Endocrinological examination revealed markedly increased serum growth hormone (GH) and prolactin (PRL), which responded paradoxically to a TRH test. In addition, the concentrations of serum dehydroepiandrosterone (DHA) and its sulfate (DHAS) were increased to adult levels, moving in accordance with changes in ACTH, which suggested that these androgens were secreted from the adrenal glands functionally. These androgens seemed to be responsible for her partial precocity. Prior reports have suggested that GH and/or PRL overproduction might have played a role in the induction of adrenarche. Also, in previous reports of 9 gigantism patients under 10 years old, the manifestation of precocious adrenarche was suggested in 8. Further investigation of the influence of GH and PRL on adrenal androgen production in children with pituitary gigantism is required. On the other hand, in short children with normal GH secretion, attention should be paid to whether or not the GH therapy in early childhood induces precocious adrenarche.     

On the regulation of sex-hormone-binding globulin--a challenge of an old dogma and outlines of an alternative mechanism

In this review, the different factors known to affect SHBG levels are discussed with respect to their possible significance in the physiological regulation of this protein: Sex steroids, puberty, nutritional status, thyroid hormones and liver disease. It is concluded that the serum levels of SHBG are related to general metabolic factors, nutritional status, growth and ageing than to the estrogen/androgen balance. The authors suggest that SHBG is regulated primarily by growth hormone, somatomedin-C and possibly other growth factors. Growth hormone may promote SHBG synthesis in the liver while somatomedin-C may stimulate its extravasation and uptake in target tissues. It is suggested that sex steroids merely have an indirect, modulating influence.     

Diverse roles for sex hormone-binding globulin in reproduction

Sex hormone-binding globulin (SHBG) transports androgens and estrogens in blood and regulates their access to target tissues. Hepatic production of SHBG fluctuates throughout the life cycle and is influenced primarily by metabolic and hormonal factors. Genetic differences also contribute to interindividual variations in plasma SHBG levels. In addition to controlling the plasma distribution, metabolic clearance, and bioavailability of sex steroids, SHBG accumulates in the extravascular compartments of some tissues and in the cytoplasm of specific epithelial cells, where it exerts novel effects on androgen and estrogen action. In mammals, the gene-encoding SHBG is expressed primarily in the liver but also at low levels in other tissues, including the testis. In subprimate species, Shbg expression in Sertoli cells is under the control of follicle-stimulating hormone and produces the androgen-binding protein that influences androgen actions in the seminiferous tubules and epididymis. In humans, the SHBG gene is not expressed in Sertoli cells, but its expression in germ cells produces an SHBG isoform that accumulates in the acrosome. In fish, Shbg is produced by the liver but has a unique function in the gill as a portal for natural steroids and xenobiotics, including synthetic steroids. However, salmon have retained a second, poorly conserved Shbg gene that is expressed only in ovary, muscle, and gill and that likely exerts specialized functions in these tissues. The present review compares the production and functions of SHBG in different species and its diverse effects on reproduction.     

La puberté surrénalienne

The androgens produced by the adrenal glands are mainly Δ5 steroids, first dehydroepiandrosterone (DHA) and its sulfate (DHAS). Adrenal androgens, very high at birth, decrease rapidly the first few months of life, remaining very low from 1 to 6 years of life. Adrenarche is defined as the changes in the pattern of adrenal secretions which occur several years before the onset of gonadal puberty (gonadarche). Developmental patterns of adrenal androgens differ markedly among species and only the chimpanzee exhibits an adrenarche comparable to that of man. Adrenarche starts in both sexes around age 7. The increase in DHA/DHAS has a rather abrupt onset and is thereafter progressive. Before the onset of gonadarche mean levels of DHA and DHAS have increased by about 10 and 20 fold respectively. The prepubertal rise in plasma Δ⁵-androgens is accompanied by that of Δ4-androstenedione and 11β-hydroxy-Δ⁴-androstenedione occurring likely at about the same time but being very progressive and more modest are only significant after age 8 in both sexes. Adrenal androgens continue to rise during puberty. Plasma levels of DHA and DHAS continue to rise from pubertal stages 1 to 5 and remain similar in both sexes until age 15. At pubertal stage P5, plasma DHA levels are similar to that seen in young adults with no sex difference while that of DHAS continue to rise in boys and become significantly higher than in girls. Developmental changes in adrenal androgen secretions are also observed in the response to ACTH stimulation. Whether estimated as absolute levels or Δ of response, the rise in all unconjugated adrenal androgens to a short or prolonged ACTH stimulation, is greater with increasing age, with no sex difference, and is somewhat correlated to basal levels. Plasma levels of DHAS do not vary significantly the 2 hours following a bolus injection of ACTH (21, 34) but its response to longterm (3-days) ACTH stimulation is also increasing with age. Morphological and functional changes in the adrenal cortex also occur during development. Focal development of aZona reticularis starts at 5 years of age, and progressively becomes continuous. The development of the zona reticularis is parallel to the increase in adrenal androgen secretions, and is completed only by age 15. This is accompanied by a rise in 17-hydroxylase and 17,20-desmolase activity in the adrenals. In a normal timing of physiological events, the onset of adrenarche occurs several years before the onset of gonadarche, 2–3 years in girls and 3–4 years in boys. This relation does not preclude that the processes are independent events. Indeed, the onset of adrenarche and gonadarche are dissociated in a variety of disorders of sexual maturation Adrenal androgen secretions are under the control of ACTH, as shown by a series of observations. However, the specific increase of adrenal androgen secretions during development without any detectable change in ACTH stimulation, the dissociation between adrenarche and gonadarche in several conditions, have led to postulate that the biochemical differentiation of the zona reticularis may require the action of an «adrenal factor» in addition to ACTH. Among the proposed «trophic» factors of adrenal androgen secretion, LH/FSH and estrogens are no longer believed to be involved. The evidences for the existence of a separate and specific pituitary cortical androgen-stimulating hormone (CASH) are not yet convincing. Prolactin, linked to nutritional status, may stimulate the activity of the adrenal hydroxysteroid sulfotransferase. The functional zonal theory» is attractive, but it does not explain why changes in adrenal androgens occur at a given age. Finally, the occurrence of familial cases of premature pubarche, the study of the changes in adrenal androgens in monozygotic or dizygotic twins and the observation that in idiopathic delayed puberty the delay in adrenarche is only one part of a generalized growth and developmental delay, strongly suggests that maturation of the adrenal cortex is regulated, at least in part, by genetic factors. The physiological importance of adrenal androgens remains a matter of controversy. Classical “dogma” dictates that adrenal androgens are responsible for pubic hair development. It has also been suggested that they contribute to somatic growth or epiphyseal advancement in childhood. This is mainly based on the observation that premature adrenarche is accompanied by premature pubarche, tall stature and advanced bone age. However, adequate androgen secretion alone does not ensure normal sexual hair development in many patients with gonadal dysgenesis. Moreover, in children with a lack or delayed adrenarche long-term treatment with DHAS at dosages such as to restore normal levels for age, failed to induce growth of sexual hair or any change in growth rate, bone maturation velocity, or to advance puberty. Although new hypotheses favour the view that Δ5-androgens, particularly Δ⁵-androstenediol, have some characteristic properties of estrogens, the physiological role of adrenal androgens, if any, remains to be established. DHAS may well be only a prohormone. There are ample evidences that all tissues possess active sulfatases which transform it into DHA, a steroid with high turn-over. Administration of DHA to experimental animals has shown beneficial effects on various endocrine-metabolic parameters, enhanced immunoprotective functions and reduced carcinogenesis. DHA prevents diabetes in genetically diabetic and obese mice. The importance ofin vivo andin vitro experimental findings is underscored by epidemiological data showing that low DHA levels are correlated with increased cardiovascular morbidity in men, breast cancer in women and a decline in immune competence. Human studies are at the moment controversial. It remains possible that DHAS influence breast cancer risk earlier in life, and/or that there are more complex interactions with other hormones or the intracellular metabolism of DHA/DHAS. Indeed, the tissue concentrations of DHAS may be important since it may act indirectly via its metabolism into estradiol or other steroids. Further long-term studies are needed to conclude whether DHA/DHAS are a youth fountain.     

Serum 5-androstene-3 beta,17 beta-diol sulphate, sex hormone binding globulin and free androgen index in girls with premature adrenarche

Serum sex hormone binding globulin (SHBG), testosterone (T), DHEA sulphate (DHEA-S), androstenedione (AD) and delta 5-androstene-3 beta,17 beta-diol sulphate (5-ADIOL-S) levels were measured by specific radioimmunoassay in 16 girls presenting with premature adrenarche (PA) and in 14 normal girls. Mean levels of steroids measured were elevated, and SHBG significantly depressed, in the girls with PA, with values (mean +/- SE) for DHEA-S (1.73 +/- 0.17 vs 0.25 +/- 0.06 mumol/l), 5-ADIOL-S (104 +/- 8 vs 31 +/- 4 nmol/l), AD (0.89 +/- 0.06 vs 0.62 +/- 0.04 nmol/l), and T (0.49 +/- 0.03 vs 0.23 +/- 0.06 nmol/l). SHBG levels were 68 +/- 6 vs 108 +/- 5 nmol/l, and the free androgen index [100 x T (nmol/l) divided by SHBG (nmol/l)] was 0.89 +/- 0.17 vs 0.22 +/- 0.01. These studies show that SHBG is depressed in girls with premature adrenarche; with the increased testosterone levels, this results in a markedly elevated free androgen index, a measure of testosterone which is bioavailable to target tissue. This may be compounded by the elevated levels of 5-ADIOL-S in girls with PA since its role may be as a prohormone for more potent androgens (testosterone, 5 alpha-dihydrotestosterone) in target tissues such as pubic skin.     

Sex steroid hormones, sex hormone-binding globulin, and obesity in men and women.

Sex steroid hormones in both males and females have been closely related to the regulation of adiposity, either through direct or indirect physiological mechanisms. Evidence also suggests a direct relationship between sex hormones and risk factors for cardiovascular disease. In the present review article, we will discuss recent studies that have examined the complex interrelationships between sex hormones, SHBG, obesity and risk factors for cardiovascular disease. Male obesity and excess abdominal adipose tissue accumulation is associated with reductions in gonadal androgen and low adrenal C19 steroid concentrations. Reduced C19 steroids are also related to an altered metabolic risk factor profile including glucose intolerance and an atherogenic dyslipidemic state. However, the concomitant visceral obese state appears as a major correlate in these associations. In women, menopause-induced estrogen deficiency and increased androgenicity are associated with increased abdominal obesity and with the concomitant alterations in the metabolic risk profile. The accelerated accretion of adipose tissue in the intra-abdominal region coincident with the onset of menopause may explain part of the increased risk of cardiovascular disease in postmenopausal women. In both men and women, plasma levels of sex hormone-binding globulin are strong correlates of obesity and risk factors for cardiovascular disease, and more importantly, the relationships between low SHBG and altered plasma lipid levels appear to be independent from the concomitant increased levels of visceral adipose tissue. SHBG concentration may, therefore, represent the most important and reliable marker of the sex hormone profile in the examination of the complex interrelation of sex steroid hormones, obesity, and cardiovascular disease risk.     

Serum androgens and sex hormone binding globulin in obese Pima Indian females

Levels of serum androgens and sex hormone binding globulin (SHBG) were measured in 20 obese Pima Indian females aged 19–44 and compared with those of normal-weight Caucasians aged 20–46. The Pima exhibited significantly decreased SHBG compared to Caucasians, but a strong effect of age on androgen levels rendered mean comparisons useless. Androstenedione (A) and dehydroepiandrosterone-sulfate (DHEA-S) decreased significantly, and testosterone (T) declined slightly with age in the Pima, whereas these androgens showed no significant decreases in Caucasians for this age range. A possible relationship of androgens to the Pima female's propensity for android obesity as well as possible effects of obesity on SHBG, androgens, and aging is discussed.     

Testicular and adrenocortical function in healthy men and in men with benign prostatic hyperplasia.

The influence of aging upon serum concentrations of testicular steroids, sex hormone binding globulin (SHBG) and pituitary hormones and on adrenal steroid levels and adrenal steroid response to ACTH was studied in 81 healthy men aged 20-87 years. These endocrine variables were also compared in 43 patients with benign prostatic hyperplasia (BPH), aged 58-89 years and in a subgroup of 41 men, aged 58-87 years, from the above mentioned reference population. The normal endocrine aging was characterized by a rise in SHBG levels, decreasing levels of testicular steroids and non-SHBG-bound testosterone (NST) and increasing gonadotropin levels and decreasing concentrations of total estrone. Adrenal androgen levels decreased in the presence of unchanged levels of cortisol and the adrenal steroid response to ACTH changed by decreasing increments in dehydroepiandrosterone (DHA) and increasing increments in 17 alpha-hydroxyprogesterone (17OHP). With the exception of the alterations in SHBG and adrenal androgens, all these changes were finished before the seventh decade of life. BPH patients had elevated levels of testosterone and NST in the presence of normal SHBG and gonadotropin levels, elevated levels of DHA and DHA sulfate (DHAS) in the presence of normal cortisol levels, a "younger" pattern of adrenal steroid response to ACTH as judged from the increments in DHA and 17OHP, elevated ratios between estrone and 4-androstene-3,17-dione suggesting an increased peripheral aromatization and subnormal prolactin levels. BPH patients may be considered as "endocrinologically younger" than healthy subjects. DHA and especially its proximate metabolite 5-androstene-3 beta, 17 beta-diol exert powerful estrogenic effects on the receptor level. Thus the elevated levels of DHA and DHAS in the BPH patients may create an hyperestrogenic condition in addition to the slight hyperandrogenicity caused by the elevated NST levels. Both endocrine aberrations may play a role in the etiology of BPH, in accordance with the dual sex steroid sensitivity of the periurethral glands.     

Exaggerated adrenarche and altered cortisol metabolism in Type 1 diabetic children

Reported literature data strongly suggest that steroid metabolism is dysregulated in Type 1 diabetes mellitus. The aim of this study was to non-invasively examine the cortisol metabolism in children with Type 1 diabetes mellitus (T1DM) in detail and to test the hypothesis that adrenarche is affected under conventional intensive insulin therapy. In 24-h urine samples of 109 patients aged 4-18 years with T1DM of more than 1 year, steroids were profiled using gas chromatography-mass spectrometry. Additionally, urinary free cortisol (UFF) and cortisone (UFE) were quantified by RIA after extraction and chromatographic purification. Data on urinary steroids from 400 healthy controls served as reference values. Enzyme activities were assessed by established steroid metabolite ratios, e.g. 5alpha-reductase and 11beta-hydroxysteroid dehydrogenase Type 2 (11beta-HSD2) by 5alpha-tetrahydrocortisol/tetrahydrocortisol and UFE/UFF, respectively. Urinary markers of adrenarche, especially dehydroepiandrosterone and its direct metabolites were elevated in patients, as were urinary 6beta-hydroxycortisol, UFE, and 11beta-HSD2 activity. However, overall cortisol secretion, as reflected by the sum of major urinary cortisol metabolites, was mostly normal and activity of 5alpha-reductase clearly reduced. Our study provides evidence for an exaggerated adrenarche in T1DM children, which may help to understand reported sequelae in female patients like hyperandrogenic symptoms. The findings also suggest a reduced cortisol inactivation via 5alpha-reductase that is not compensated by a fall in cortisol secretion. Whether the elevated urinary 6beta-hydroxycortisol and cortisone excretion, observed in the patients, are also present in other forms of hypercortisolism and may thus serve as non-invasive clinical stress markers deserves further study.     

Pathophysiology of sex hormone binding globulin (SHBG): Relation to insulin

In humans, the plasma level of sex hormone binding globulin (SHBG) is regulated by several hormones. We have now accumulated evidence that SHBG is also intimately related to nutritional state. However, we do not yet know what specific signal, if any, may be the regulator of SHBG.

There is a strong and negative correlation between fasting insulin level and SHBG in obese as in hyperandrogenic women. Under such circumstances, a high fasting insulin level, normal glycemia and a low SHBG level suggest insulin resistance in terms of glucose disposal but not in terms of SHBG inhibition. This is a rather complex situation.

It is too early to judge the importance of IGF-I in the regulation of SHBG. But it may turn out that IGF-I is the main regulator of SHBG and that, by interaction with the IGF-I receptors, insulin carries on its inhibitory activity on SHBG.     

Sex hormone-binding globulin (SHBG) and estradiol cross-talk in breast cancer cells.

Sex hormone-binding globulin (SHBG) is a plasma glycoprotein that regulates the action of steroid hormones at several levels. SHBG regulates the availability of free androgens and estradiol to hormone-responsive tissues. Moreover, SHBG is also part of a novel steroid signaling system. We report here on the mechanism of action and the biological effects of SHBG in breast cancer cells, especially distinguishing cross-talk between membrane-initiated SHBG and estradiol pathways. After interacting with a specific binding site on breast cancer cell membranes, SHBG activates a specific pathway, and by cAMP induction, inhibits estradiol-mediated activation of ERK. Both estradiol and SHBG membrane-initiated pathways involve cross-talk at MAP kinase level with the ultimate result of inhibiting estradiol-mediated cell growth and antiapoptosis. On the basis of reported evidence, we suggest that SHBG is one of the regulators of growth and apoptosis of estrogen-dependent breast cancer cells.     

The control of the interaction of sex hormone-binding globulin with its receptor by steroid hormones

Sex hormone-binding globulins (SHBG) is a plasma glycoprotein that binds certain steroids. It, in turn, binds to a specific receptor on cell membranes. This work was undertaken to investigate the role of steroids in the interaction of SHBG with its receptor. Because the probe for the interaction of SHBG with its receptor is 125I-SHBG, we first showed that 125I-SHBG binds [3H]dihydrotestosterone (DHT) at 4 degrees C and 37 degrees C with KD values similar to those published previously for pure radioinert SHBG. 125I-SHBG could be prevented from binding to its receptor by a variety of steroids whose relative inhibitory activity (dihydrotestosterone much greater than 2-methoxyestradiol greater than testosterone greater than estradiol much greater than methyltrienolone greater than cortisol) was almost identical to their relative ability to bind to SHBG. Because significant binding of [3H]DHT to the SHBG receptor could not be demonstrated, steroid inhibition of SHBG binding must be noncompetitive. If steroids bound to SHBG prevent binding to the SHBG receptor, then liganded SHBG should have a higher apparent KD for its receptor than unliganded SHBG. This is the case. The KD was 0.86 +/- 0.25 nM for the high affinity receptor site using liganded SHBG and 0.19 +/- 0.024 nM for unliganded SHBG. Thus, only liganded SHBG assumes a conformation that prohibits interaction with the SHBG receptor. However, when unliganded SHBG was prebound to its receptor, it retained its ability to bind [3H] DHT. The model that emerges from these observations is as follows. Unliganded SHBG can bind either steroids or receptor in a reversible reaction; SHBG bound to a steroid cannot bind to the receptor, but unliganded SHBG that first binds to the receptor can subsequently bind steroids.     

Adrenal steroidogenic defects in children with precocious pubarche.

The occurrence of nonclassical congenital adrenal hyperplasia among children with precocious pubarche is still a matter of debate. We studied the adrenal steroid response to ACTH stimulus (Synacthen, 0.25 mg i.v. bolus) in 26 Italian children (5 boys, 21 girls) who had presented pubic hair, without other signs of virilization, at ages ranging between 0.45 and 8.8 years. The control groups comprised 8 prepubertal children (5 boys, 3 girls) and 12 children at Tanner stage 2 for pubic hair development (1 boy, 11 girls). Two patients were diagnosed as having nonclassical congenital adrenal hyperplasia: 1 due to 21-hydroxylase deficiency, the other due to 3 beta-hydroxysteroid-dehydrogenase deficiency. The remainder, classified as having idiopathic precocious pubarche (PP), had adrenal androgens higher than normal prepubertal children and similar levels to those observed in early pubertal controls. In contrast to a recent report, we confirmed that mild adrenal enzymatic defects can occur in PP, and, consequently, the use of ACTH testing in children with PP seems to be recommended.     

Sex hormone-binding globulin and female reproductive function

Although sex steroids have long been known to influence serum concentrations of SHBG, it is now recognized that nutritional factors may be more important in the regulation of SHBG in women. Thus, SHBG concentrations are negatively correlated with body mass index (BMI) and, more particularly, to indices of central adiposity. Polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility, is associated with truncal obesity, hyperandrogenism and hyperinsulinaemia. There is evidence that insulin may be the humoral mediator of the weight-dependent changes in SHBG. Serum SHBG concentrations are inversely correlated with both fasting and glucose-stimulated insulin levels, and insulin has been shown to have a direct inhibitory effect on SHBG synthesis and secretion by hepatocytes in culture. However, the interrelationship of BMI, insulin and SHBG appears to be different in women with PCOS from that in normal subjects. The clinical importance of the weight-related suppression of SHBG is illustrated by the finding of a greater prevalence of hirsutism in obese women with PCOS compared with their lean counterparts. Obese subjects with PCOS have similar total testosterone concentrations to lean PCO women but have lower SHBG and reciprocally higher free testosterone levels. Calorie restriction results in reduction of serum insulin followed by an increase in SHBG and a fall in free testosterone but an isocaloric, low-fat diet has no significant effect on SHBG concentrations. Weight reduction in obese, hyperandrogenaemic women with PCO is an important approach to the management of both anovulation and hirsutism.     

Sex hormone-binding globulin, its membrane receptor, and breast cancer: a new approach to the modulation of estradiol action in neoplastic cells

The role of human Sex Hormone-Binding Globulin (SHBG), the plasma carrier of sex steroids, and its membrane receptor, SHBG-R, in estrogen-dependent breast cancer has been investigated in our laboratory in the past few years. SHBG-R is expressed in MCF-10 A cells (not neoplastic mammary cells), MCF-7 cells (breast cancer, ER positive) and in tissue samples from patients affected with ER positive breast cancer, but not in estrogen-insensitive MDA-MB 231 cells. The SHBG/SHBG-R interaction, followed by the binding of estradiol to the complex protein/receptor, causes a significant increase of the intracellular levels of cAMP, but does not modify the amount of estradiol entering MCF-7 cells. The estradiol-induced proliferation of MCF-7 cells is inhibited by SHBG, through SHBG-R, cAMP and PKA. Similarly, the proliferation rate of tissue samples positive for SHBG-R was significantly lower than the proliferation rate of negative samples. SHBG and SHBG-R could thus trigger a ‘biologic’ anti-estrogenic pathway. In order to get a more detailed knowledge of this system, we first examined the frequence of the reported mutated form of SHBG in 255 breast cancer patients. The mutated SHBG is characterized by a point mutation (Asp 327→Asn) causing an additional N-glycosylation site, which does not affect the binding of steroids to SHBG. The frequence of the mutation was significantly higher (24.5%) in estrogen-dependent breast cancers than in healthy control subjects (11.6%). This observation confirms the close relationship between SHBG and estrogen-dependent breast cancer and suggests that the mutation could modify SHBG activity at cell site. Lastly, the possibility of using SHBG to modulate the estradiol action in breast cancer was further studied by transfecting MCF-7 cells with an expression vector carrying the SHBG cDNA (study in collaboration with G.L. Hammond). Transfected cells are able to produce significant amount of SHBG in their medium, but their SHBG-R is reduced to undetectable levels. The SHBG produced by transfected MCF-7 cells is, however, able to inhibit estradiol-induced proliferation of MCF-7 cells expressing a functional receptor. Thus, the local production of SHBG obtained with transfection could be a useful tool to control cell growth in estrogen-dependent breast cancer.     

Changes in steroid pattern following acute and chronic adrenocorticotropin administration in premature adrenarche

Biochemically adrenarche is characterized by increased production of 5-ene steroids, in particular Dehydroepiandrosterone (DHA) and its sulphate (DHA-S). It is still not clear if ACTH is responsible for this adrenal steroid production. The aim of the present study was to evaluate the effect of acute and chronic ACTH administration, without dexamethasone pretreatment, on hormonal patterns in 20 patients (5 males aged between 6 8/12 and 7 10/12 years and 15 females aged between 5 9/12 and 7 6/12 years) with idiopathic premature adrenarche. Pregnenolone (5P), DHA, DHA-S, 17-hydroxyprogesterone (17-OHP), androstenedione (A), 11-deoxycortisol (S) and cortisol (F) have been determined by Radioimmunoassay. The results of the hormonal evaluation (means +/- standard error) showed high plasma levels of DHA [329.2 +/- 41.7 ng/100 ml (dl)] and DHA-S (169.1 +/- 54 micrograms/dl) and slightly increased levels of 5P (74.4 +/- 7.1 ng/dl), of A (45.4 +/- 4.6 ng/dl) and 17-OHP (69.3 +/- 11.3 ng/dl) in comparison to those of controls, thus indicating a decrease in 3 beta-hydroxysteroid dehydrogenase activity and an increase in 17-20-lyase and 17-hydroxylase activities, characteristic for adrenarche. Acute and chronic ACTH stimulation did not amplify the characteristic basal hormonal pattern, but they induced a shift of adrenal steroid metabolism to 4-ene pathway, suggesting that the basal hormonal pattern in premature adrenarche may be independent or, at least, not exclusively dependent on ACTH control.