Receptors for insulin and insulin-like growth factor-I in the human adrenal gland

Role of the Adrenal Medulla in Hypoglycaemia-Associated Autonomic Failure-A Diabetic Perspective

Hypoglycaemia-associated autonomic failure (HAAF) is characterised by an impairment in adrenal medullary and neurogenic symptom responses following episodes of recurrent hypoglycaemia. Here, we review the status quo of research related to the regulatory mechanisms of the adrenal medulla in its response to single and recurrent hypoglycaemia in both diabetic and non-diabetic subjects with particular focus given to catecholamine synthesis, enzymatic activity, and the impact of adrenal medullary peptides. Short-term post-transcriptional modifications, particularly phosphorylation at specific residues of tyrosine hydroxylase (TH), play a key role in the regulation of catecholamine synthesis. While the effects of recurrent hypoglycaemia on catecholamine synthetic enzymes remain inconsistent, long-term changes in TH protein expression suggest species-specific responses. Adrenomedullary peptides such as neuropeptide Y (NPY), galanin, and proenkephalin exhibit altered gene and protein expression in response to hypoglycaemia, suggesting a potential role in the modulation of catecholamine secretion. Of note is NPY, since its antagonism has been shown to prevent reductions in TH protein expression. This review highlights the need for further investigation into the molecular mechanisms involved in the adrenal medullary response to hypoglycaemia. Despite advancements in our understanding of HAAF in non-diabetic rodents, a reliable diabetic rodent model of HAAF remains a challenge.

Prevalence and incidence of type 2 diabetes mellitus in patients with adrenal incidentalomas: a study of 709 cases

AIM

To evaluate the prevalence and incidence of type 2 diabetes in patients with nonfunctioning adrenal incidentalomas (NFAI) or adrenal incidentalomas (AI) with autonomous cortisol secretion (ACS).

METHODS

In this single-center retrospective study, all patients with adrenal incidentalomas ≥1 cm and ACS or NFAI studied between 2013 and 2020 were included. ACS was defined by a post-dexamethasone suppression test (DST) serum cortisol concentration ≥1.8 μg/dl, in the absence of signs of hypercortisolism, and NFAI was defined as a DST < 1.8 μg/dl without biochemical evidence of hypersecretion of other hormones.

RESULTS

Inclusion criteria were met by 231 patients with ACS and 478 with NFAI. At diagnosis, type 2 diabetes was present in 24.3% of patients. No differences were found in the prevalence of type 2 diabetes (27.7 vs. 22.6%, P = 0.137) between patients with ACS and NFAI. However, fasting plasma glucose values and glycated hemoglobin levels were significantly higher in patients with ACS than with NFAI (112 ± 35.6 vs. 105 ± 29 mg/dl, P = 0.004; and 6.5 ± 1.4 vs. 6.1 ± 0.9%, P = 0.005, respectively). Furthermore, patients with type 2 diabetes had higher urinary free cortisol (P = 0.039) and late-night salivary cortisol levels (P = 0.010) than those without type 2 diabetes. After a median follow-up of 28 months, no differences were found in the incidence of type 2 diabetes between the groups (HR 1.17, 95% 0.52-2.64).

CONCLUSION

Type 2 diabetes was present in one fourth of our cohort. We found no differences in its prevalence or incidence between the groups. However, glycemic control might be worse among diabetic patients with ACS. Higher concentrations of urinary and salivary cortisol were found in patients with than without type 2 diabetes.

Insulin resistance and adrenal incidentalomas: A bidirectional relationship

An adrenal incidentaloma (AI) is an adrenal mass incidentally found via a radiological modality, independent of an endocrinological investigation. In this review, we aimed to investigate the possible reasons behind the increased frequency in AI detection, especially in ageing populations. The pathophysiological effects of insulin resistance (IR), hyperinsulinemia and various anabolic pathways are analyzed. In addition, we review data from studies indicating an increased incidence of adrenal adenomas and carcinomas in patients with type 2 diabetes mellitus (T2DM). The establishment of obesity as a global epidemic, with a higher prevalence in the female than in the male population, coincide with data regarding AIs and the conditions may share a pathophysiological basis. Furthermore, we discuss the bidirectional association of AIs with obesity, insulin resistance and T2DM, especially in patients with autonomous cortisol secretion. Lastly, as per the definition of an AI, we touch upon the evolution of radiological imaging as another possible cause of the rise in prevalence of AIs, especially concerning the greater use and precision of computed tomography (CT).

Luteinizing hormone and insulin resistance in menopausal patients with adrenal incidentalomas: The cause-effect relationship?

OBJECTIVE

A high prevalence of insulin resistance (IR) has proven to manifest in patients with adrenal incidentalomas (AI). It has been demonstrated that an increase in IR is related to the size of tumourous masses; additionally, luteinizing hormone (LH)-dependent adrenal pathologies are well documented in patients with LH-responsive adrenal tumours occurring under conditions of physiologically elevated LH. We hypothesized that an association between LH and insulin might play a role in adrenal tumourigenesis and steroidogenesis.

DESIGN

The aim of our study was to investigate the association between LH and IR; adrenal tumour size (ATS) and IR; LH and cortisol after the 1 mg overnight dexamethasone test (1 mg DST); and ATS and 1 mg DST cortisol in AI patients. This was a case-control study conducted in the Clinic for Endocrinology, Diabetes and Metabolic Diseases in Belgrade, Serbia. The total study group consisted of 105 menopausal women: 75 AI patients [27 with nonfunctional AI (NAI) and 48 with (possible) autonomous cortisol secretion ((P)ACS)] and 30 age-, BMI-, LH- and menopause duration-matched healthy control (HC) women. To estimate IR, we used homeostasis model assessment (HOMA-IR).

RESULTS

Luteinizing hormone and ATS are in a significant positive correlation with HOMA-IR and 1 mg DST cortisol in menopausal patients with AI and (P)ACS.

CONCLUSIONS

Our data point to a possible cause-effect relationship between LH and insulin in patients with AI and (P)ACS adding to the body of evidence of their involvement in adrenal tumourigenesis and steroidogenesis.

Adrenocortical tumors and insulin resistance: What is the first step?

The pathogenetic mechanisms underlying the onset of adrenocortical tumors (ACTs) are still largely unknown. Recently, more attention has been paid to the role of insulin and insulin-like growth factor (IGF) system on general tumor development and progression. Increased levels of insulin, IGF-1 and IGF-2 are associated with tumor cell growth and increased risk of cancer promotion and progression in patients with type 2 diabetes. Insulin resistance and compensatory hyperinsulinemia may play a role in adrenal tumor growth through the activation of insulin and IGF-1 receptors. Interestingly, apparently non-functioning ACTs are often associated with a high prevalence of insulin resistance and metabolic syndrome. However, it is unclear if ACT develops from a primary insulin resistance and compensatory hyperinsulinemia or if insulin resistance is only secondary to the slight cortisol hypersecretion by ACT. The aim of this review is to summarize the current evidence regarding the relationship between hyperinsulinemia and adrenocortical tumors.

Contraception, and pregnancy in adolescents with type 1 diabetes: a review

Adolescence is a critical period for girls with type 1 diabetes mellitus (T1D). Reproductive issues, such as menstrual abnormalities, risk of an unplanned pregnancy, and contraception, should be addressed during this phase of life. This paper reviews several reproductive issues that are important in the care of adolescents, including pubertal development, menstrual abnormalities, ovulatory function, reproductive problems, the effects of hyperglycemia, contraception, and treatment of an unplanned pregnancy. A review of the literature was conducted. A MEDLINE search January 1966 to March 2011 was performed using the following MESH terms: puberty, menarche, ovary, polycystic ovary syndrome, menstruation, contraception, contraception-barrier, contraceptives-oral-hormonal, sex education, family planning services, and pregnancy in adolescence. This literature search was cross-referenced with an additional search on diabetes mellitus-type 1, diabetes complications, and pregnancy in diabetes. All published studies were searched regardless of the language of origin. Bibliographies were reviewed to extract additional relevant sources.

Circulating androgens in women: exercise-induced changes

Physical exercise is known to strongly stimulate the endocrine system in both sexes. Among these hormones, androgens (e.g. testosterone, androstenedione, dehydroepiandrosterone) play key roles in the reproductive system, muscle growth and the prevention of bone loss. In female athletes, excessive physical exercise may lead to disorders, including delay in the onset of puberty, amenorrhoea and premature osteoporosis. The free and total fractions of circulating androgens vary in response to acute and chronic exercise/training (depending on the type), but the physiological role of these changes is not completely understood. Although it is commonly accepted that only the free fraction of steroids has a biological action, this hypothesis has recently been challenged. Indeed, a change in the total fraction of androgen concentration may have a significant impact on cells (inducing genomic or non-genomic signalling). The purpose of this review, therefore, is to visit the exercise-induced changes in androgen concentrations and emphasize their potential effects on female physiology. Despite some discrepancies in the published studies (generally due to differences in the types and intensities of the exercises studied, in the hormonal status of the group of women investigated and in the methods for androgen determination), exercise is globally able to induce an increase in circulating androgens. This can be observed after both resistance and endurance acute exercises. For chronic exercise/training, the picture is definitely less clear and there are even circumstances where exercise leads to a decrease of circulating androgens. We suggest that those changes have significant impact on female physiology and physical performance.

The relation of adiponectin and tumor necrosis factor alpha levels between endothelial nitric oxide synthase, angiotensin-converting enzyme, transforming growth factor beta, and tumor necrosis factor alpha gene polymorphism in adrenal incidentalomas

OBJECTIVE

The aim of our study was to demonstrate demographic characteristics, presence of inflammatory markers, distribution of angiotensin-converting enzyme (ACE), tumor necrosis factor (TNF), endothelial nitric oxide synthase (eNOS) genotypes and relations among these parameters in these patients and control subjects.

RESEARCH DESIGN AND METHODS

Study samples were collected from 50 patients with adrenal mass and 30 control groups. The eNOS, ACE, TNF-alpha, transforming growth factor (TGF)-beta genes polymorphisms, TNF-alpha, adiponectin levels were analysed in 50 unrelated Turkish patients with a diagnosis of adrenal incidentaloma (AI).

RESULTS

There was statistically significant difference between TNF-alpha levels of patient and controls (p=0.048). We have not detected the connection between TGF-beta, TNF-alpha, ACE, eNOS gene polymorphism with serum TNF-alpha and adiponectin levels. In this study, we demonstrated that there were significant differences for ACE genotypes in the patients when compared to the controls (p<0.05). The percentages of the ID, DD, II genotypes for ACE gene polymorphism in the patients group were 30.0, 13.0, 7.0%, respectively.

CONCLUSIONS

According to different cases of eNOS, TGF-beta, ACE, and TNF-alpha gene genotypes; no statistical significant difference was found between basal cortisol, ACTH, DHEAS, metanephrine, renin, aldosterone, normetanephrine, 17-hydroxyprogesterone, 1 mg low-dose dexamethasone suppression test-cortisol response and AI size. In this study, I/D genotype was determined to be statistically higher in ACE gene in patients with AI (p=0.014).

Body fat and animal protein intakes are associated with adrenal androgen secretion in children

BACKGROUND

Adrenarche is the increase in adrenal androgen (AA) production starting in childhood. Until now, it has been unknown whether or not nutritional factors modulate adrenarche.

OBJECTIVE

The objective was to examine whether body composition and certain dietary intakes are associated with AA production in children after accounting for urinary indicators of major adrenarche-related steroidogenic enzymes.

DESIGN

Androgen and glucocorticoid metabolites were profiled by gas chromatography-mass spectrometry in 24-h urine samples of 137 healthy prepubertal children aged 3-12 y, for whom birth characteristics, growth velocity data, and 3-d weighed-diet record information were available. Associations of the sum of C19 metabolites (reflecting daily AA secretion) with nutritional factors [fat mass (FM), fat-free mass (FFM), nutrient intakes, glycemic index, and glycemic load] and AA-relevant estimates of steroidogenic enzyme were examined in stepwise multiple regression models adjusted for age, sex, urine volume, and total energy intake. Enzyme activity estimates were calculated by using specific urinary steroid metabolite ratios.

RESULTS

Of the nutrition-relevant predictors, FM (P < 0.0001) explained most of the variation of AA secretion (R(2) = 5%). Animal protein intake was also positively associated with AA secretion (P < 0.05), which explained 1% of its variation. FFM (P = 0.1) and total protein intake (P = 0.05) showed positive trends. The difference in daily AA secretion between the lowest and highest quartile of FM was comparable to that between the lowest and highest estimated activity of one of the major steroidogenic enzymes.

CONCLUSIONS

Body fat mass may relevantly influence prepubertal adrenarchal androgen status. In addition, animal protein intake may also make a small contribution to AA secretion in children.

Brain insulin infusion does not augment the counterregulatory response to hypoglycemia or glucoprivation

Although high dosages of insulin can cause hypoglycemia, several studies suggest that increased insulin action in the head may paradoxically protect against severe hypoglycemia by augmenting the sympathoadrenal response to hypoglycemia. We hypothesized that a direct infusion of insulin into the third ventricle and/or the mediobasal hypothalamus (MBH) would amplify the sympathoadrenal response to hypoglycemia. Nine-week-old male rats had insulin (15 mU) or artificial cerebrospinal fluid (aCSF, control) infused bilaterally into the MBH or directly into the third ventricle. During the final 2 hours of the brain insulin or aCSF infusions, the counterregulatory response to either a hyperinsulinemic hypoglycemic (approximately 50 mg/dL) clamp or a 600-mg/kg intravenous bolus of 2-deoxyglucose (2DG) was measured. 2-Deoxyglucose was used to induce a glucoprivic response without peripheral insulin infusion. In response to insulin-induced hypoglycemia, epinephrine rose more than 60-fold, norepinephrine rose more than 4-fold, glucagon rose 8-fold, and corticosterone rose almost 2-fold; but these increments were not different in aCSF vs insulin treatment groups with either intracerebroventricular or bilateral MBH insulin protocols. Intracerebroventricular insulin infusion stimulated insulin signaling as noted by a 5-fold increase in AKT phosphorylation. In the absence of systemic insulin infusion, 2DG-induced glucopenia resulted in an equal counterregulatory response with brain aCSF and insulin infusions. Under the conditions studied, although insulin infusion acted to stimulate hypothalamic insulin signaling, neither intrahypothalamic nor intracerebroventricular insulin infusion augmented the counterregulatory response to hypoglycemia or to 2DG-induced glucoprivation. Therefore, it is proposed that the previously noted acute actions of insulin to augment the sympathoadrenal response to hypoglycemia are likely mediated via mechanisms exterior to the central nervous system.

Biological factors and the determination of androgens in female subjects

The idea of the presence of androgens in females may sound peculiar as androgens generally refer to male hormones. Although produced in small amounts in women, androgens have direct and significant effects on many aspects of female physiology. Moreover, androgens are precursors to estrogens, which are the predominant female sex hormones. The measurement of androgens in blood is important in the diagnosis of both gonadal and adrenal functional disturbances, as well as monitoring subsequent treatments. The accuracy of such measurements is crucial in sports medicine and doping control. Therefore, the concentration of androgens in female subjects is frequently measured. Analysing such compounds with accuracy is especially difficult, costly and time consuming. Therefore, laboratories widely use direct radioimmunoassay kits, which are often insensitive and inaccurate. It is especially complicated to determine the level of androgens in women, as the concentration is much lower compared to the concentration found in males. Additionally, the amount of androgens in fluids tends to decrease with aging. Analyses of hormone concentrations are influenced by a myriad of factors. The factors influencing the outcome of these tests can be divided into in vivo preanalytical factors (e.g., aging, chronobiological rhythms, diet, menstrual cycle, physical exercise, etc.), in vitro preanalytical factors (e.g., specimen collection, equipment, transport, storage, etc.) and as mentioned before, analytical factors. To improve the value of these tests, the strongly influencing factors must be controlled. This can be accomplished using standardised assays and specimen collection procedures. In general, sufficient attention is not given to the preanalytical (biological) factors, especially in the measurement of androgens in females. Biological factors (non-pathological factors) that may influence the outcome of these tests in female subjects have received little attention and are the topic of the present review.

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.

Pubertal and gender-related changes in the sympathoadrenal system in healthy children

A critical amount of body fat is necessary for the initiation of puberty, and leptin, an adipocyte-derived hormone, is necessary for pubertal development. The sympathoadrenal system modulates body fat stores and leptin secretion and interacts with adrenocortical androgen production, suggesting a possible role in sexual maturation. We studied sympathetic nerve and adrenomedullary activity at rest in 80 healthy children (ages, 5-17 yr; 37 boys and 43 girls) in relation to age, pubertal stage, gender, physical activity, body mass index, and serum levels of sex steroids, dehydroepiandrosterone sulfate, cortisol, leptin, and insulin. Plasma concentrations of the adrenomedullary hormone, epinephrine (E), and its metabolite metanephrine (MN), decreased significantly with advancing puberty and were higher in boys than in girls. E and MN correlated significantly and inversely with dehydroepiandrosterone sulfate, estradiol, testosterone, leptin, and insulin. Plasma norepinephrine, which is primarily derived from sympathetic nerve endings, increased significantly with advancing puberty and increasing testosterone levels in boys. Stepwise multiple regression analysis revealed that E was best predicted by pubertal stage and leptin, and MN by estradiol and leptin. Our data suggest that sympathoadrenal hormones may play a role in the complex process of sexual maturation. Further studies are needed to investigate a possible modulatory role of the adrenal medulla in the body weight-related timing of adrenarche and/or gonadarche.

Ovarian and adrenal steroid production: regulatory role of LH/HCG

BACKGROUND

The contribution of the adrenal glands to the total circulating steroid pool in women is not well known. There is evidence that human adrenals express the LH receptor gene and that LH may affect adrenal androgen secretion.

METHODS

HCG stimulation tests (a single dose of 5000 IU i.m.) were performed in women at reproductive age (group 1, n = 6, age 21--39 years) before and after treatment with a GnRH agonist for 3 weeks, and in oophorectomized post-menopausal women (group 2, n = 6, 47--59 years) during and after estrogen replacement therapy (ERT).

RESULTS

HCG did not stimulate the secretion of cortisol, dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulphate (DHEAS) in group 2. In contrast, in group 1, the basal concentrations of serum 17-hydroxyprogesterone (17-OHP), androstenedione, testosterone and estradiol (E(2)) were stimulated significantly (17-OHP 105%, androstenedione 31%, testosterone 20%, E(2) 136%) by HCG, and the treatment with GnRH agonist decreased the responses. The basal serum concentrations of these steroids were significantly lower in oophorectomized women (17-OHP 57%, androstenedione 46%, testosterone 25%), and HCG did not increase these levels. It can be approximated that the ovarian contribution to the circulating levels of 17-OHP, androstenedione and testosterone is 25--30%, and that the adrenals are the primary source of cortisol, DHEA and DHEAS.

CONCLUSION

LH/HCG does not have a major role in the regulation of adrenal steroid synthesis in endocrinologically healthy women.

The role of the adrenal cortex in polycystic ovary syndrome

Adrenal androgen excess affects approximately 25% of PCOS patients. The exact etiology of this excess in PCOS patients is unclear. Some evidence that adrenal androgen excess may be a genetic trait. The adrenal androgen response to ACTH is highly individualized, and the relative response seems to be constant over time. In addition, there is a strong familial component to adrenal androgen levels in normal individuals and PCOS patients. It is possible that the tendency to overproduce adrenal androgens is an inherited risk factor for the development of PCOS. Overall, few hyperandrogenic patients actually have isolated deficiencies of 3 beta-hydroxysteroid dehydrogenase, 21-hydroxylase, and 11-hydroxylase. The ovarian hormonal secretion in PCOS can affect adrenal androgen secretion and metabolism, although this factor accounts for only part of this abnormality. More likely, the adrenal androgen excess results from a generalized hyperresponsiveness of the adrenal cortex to ACTH, but without an increase in CRH or ACTH sensitivity. Although glucocorticoid administration may improve the ovulatory function of these patients, the results are modest and cannot be predicted by the circulating androgen levels.

DHEA-S levels in hypopituitaric patients with severe GH deficiency are strongly reduced across lifespan. Comparison with IGF-I levels before and during rhGH replacement

Both IGF-I and DHEA-S undergo an age-related decrease and their decrease could be involved in age-related changes in body composition, structure functions and metabolism. On the other hand, it is well known that mean IGF-I levels are clearly reduced in hypopituitaric patients with GH deficiency (GHD) while data about dehydroepiandrosterone sulfate (DHEA-S) levels in hypopituitarism are scanty. We evaluated DHEA-S and IGF-I levels and their relationship in 90 patients with panhypopituitarism (HYPOPIT) with severe GHD [49 women and 41 men; age, mean+/-SE: 47.9+/-1.49 yr, range: 20-80 yr, BMI: 26.4+/-0.6 kg/m2; 21 with childhood-onset (CO) and 69 with adult-onset (AO) HYPOPIT]. DHEA-S and IGF-I levels were also evaluated in 24 HYPOPIT with GHD after 3-month recombinant human GH (rhGH) replacement. Data in HYPOPIT were compared with those in a large group of healthy controls (NS, 233 women and 103 men, aged 20-80 yr; all subjects were within +/-15% of their ideal body weight). In NS both DHEA-S levels and IGF-I were gender-independent while showed a strong, inverse correlation with age (r=-0.6; p<0.001 and r=-0.56; p<0.0001, respectively). Nevertheless, no relationship was found between DHEA-S and IGF-I levels in NS. In HYPOPIT, age-adjusted mean DHEA-S and IGF-I levels were clearly lower than those in NS (2.3+/-0.4 vs 16.0+/-0.7 microg/l, p<0.005; 71.1 +/- 4.5 vs 170+/-4.7 microg/l, p<0.005). IGF-I levels in CO-HYPOPIT were lower (p<0.01) than those in AO-HYPOPIT (49.6+/-4.8 vs 77.0+/-5.4 microg/l), while DHEA-S levels were similar in both subgroups (2.6+/-0.7 vs 2.3+/-0.4 microg/l). In HYPOPIT both DHEA-S and IGF-I were independent of age and gender while there was a trend toward a positive association between each other (r=0.45; p<0.003). Analyzing individual levels in HYPOPIT with respect to age-adjusted normal ranges, IGF-I levels were below normal in 84, 62 and 0% between 20-40, 40-60 and 60-80 yr, respectively. On the other hand, DHEA-S levels were below normal in 84, 86 and 67% between 20-40, 40-60 and 60-80, respectively. In HYPOPIT rhGH treatment strikingly increased IGF-I levels (150+/-3.2 vs 85.3+/-4.1 microg/l, p<0.005) while did not modify DHEA-S levels (1.7+/-0.2 vs 1.6+/-0.2 microg/l). In conclusion, our results demonstrate that DHEA-S and IGF-I are negatively and independently associated to age in physiological conditions but not in hypopituitaric patients in whom both are strikingly reduced. Both DHEA-S and IGF-I levels in HYPOPIT show some overlap with those in normal subjects; thus the assay of these parameters is not diagnostic for hypopituitarism. DHEA-S reduction in HYPOPIT does not depend on IGF-I as indicated also by evidence that GH replacement restores IGF-I but does not modify DHEA-S levels.

Immunodetection of Insulin-Like Growth Factor I (IGF-l) in Normal and Pathological Adrenocortical Tissue

IGF-I is one of the peptides that participates in normal adrenocortical cell growth and, possibly, in the genesis and/or maintenance of tumors and hyperplasias of the adrenal cortex. An immunohistochemical technique was used for the analysis of IGF-l expression in eight control and four hyperplastic adrenals, 11 adrenal cortical adenomas, and 18 adrenal cortical carcinomas. A large number of IGF-I positive cells with granular cytoplasmic (GC) staining pattern was found in the reticularis layer of control adrenal tissues. Fifty percent of the hyperplasias had the GC pattern and the other 50% a mixed pattern; in 64% of the tumors, the adenomas showed a LM (linear membrane) pattern, while adenocarcinomas usually showed a GC pattern (94%). Approximately 75% of the hyperplasias had between 10 and 50% of IGF-l positive cells, while adenomas and carcinomas had over 50% of IGF-I positive cells in 64% and 83% of the samples, respectively. The size of the tumors with 50% positive cells, compared with those with less than 50%, was, on average, greater, but no statistical differences between cell positivity and corresponding clinical syndrome were observed. Thus, detection of IGF-l in control and pathological adrenal tissue suggests participation of this growth factor in cell function and/or growth and proliferation.

Developmental and functional biology of the primate fetal adrenal cortex

The unique characteristics of the primate (particularly human) fetal adrenal were first realized in the early 1900s when its morphology was examined in detail and compared with that of other species. The unusual architecture of the human fetal adrenal cortex, with its unique and disproportionately enlarged fetal zone, its compact definitive zone, and its dramatic remodeling soon after birth captured the interest of developmental anatomists. Many detailed anatomical studies describing the morphology of the developing human fetal adrenal were reported between 1920 and 1960, and these morphological descriptions have not changed significantly. More recently, it has become clear that fetal adrenal cortical growth involves cellular hypertrophy, hyperplasia, apoptosis, and migration and is best described by the migration theory, i.e. cells proliferate in the periphery, migrate centripetally, differentiate during their migration to form the functional cortical zones, and then likely undergo apoptosis in the center of the cortex. Consistent with this model, cells of intermediate phenotype, arranged in columnar cords typical of migration, have been identified between the definitive and fetal zones. This cortical area has been referred to as the transitional zone and, based on the expression of steroidogenic enzymes, we consider it to be a functionally distinct cortical zone. Elegant experiments during the 1950s and 1960s demonstrated the central role of the primate fetal adrenal cortex in establishing the estrogenic milieu of pregnancy. Those findings were among the first indications of the function and physiological role of the human fetal adrenal cortex and led Diczfalusy and co-workers to propose the concept of the feto-placental unit, in which DHEA-S produced by the fetal adrenal cortex is used by the placenta for estrogen synthesis. Tissue and cell culture techniques, together with improved steroid assays, revealed that the fetal zone is the primary source of DHEA-S, and that its steroidogenic activity is regulated by ACTH. In recent years, function of the human and rhesus monkey fetal adrenal cortical zones has been reexamined by assessing the localization and ontogeny of steroidogenic enzyme expression. The primate fetal adrenal cortex is composed of three functionally distinct zones: 1) the fetal zone, which throughout gestation does not express 3 beta HSD but does express P450scc and P450c17 required for DHEA-S synthesis; 2) the transitional zone, which early in gestation is functionally identical to the fetal zone but late in gestation (after 25-30 weeks) expresses 3 beta HSD, P450scc, and P450c17, and therefore is the likely site of glucocorticoid synthesis, and 3) the definitive zone, which lacks P450c17 throughout gestation but late in gestation (after 22-24 weeks) expresses 3 beta HSD and P450scc, and therefore is the likely site of mineralocorticoid synthesis. Indirect evidence, based on effects of P450c21 deficiency and maternal estriol concentrations, indicate that the fetal adrenal cortex produces cortisol and DHEA-S early in gestation (6-12 weeks). However, controversy exists as to whether cortisol is produced de novo or derived from the metabolism of progesterone, as data regarding the expression of 3 beta HSD in the fetal adrenal cortex early in gestation are conflicting. During the 1960s, Liggins and colleagues demonstrated that in the sheep, cortisol secreted by the fetal adrenal cortex late in gestation regulates maturation of the fetus and initiates the cascade of events leading to parturition. Those pioneering discoveries provided insight into the mechanism underlying the timing of parturition and therefore were of particular interest to obstetricians and perinatologists confronted with the problems of preterm labor. However, although cortisol emanating from the fetal adrenal cortex promotes fetal maturation in primates as it does in sheep, its role in the regulation of primate parturition, unlike that in sheep

Peptide growth factors and the adrenal cortex

Increasing evidence suggests that the actions of classical stimulants of adrenocortical growth and function, such as ACTH or dietary sodium restriction, may partially be mediated via locally produced regulators. Several peptide growth factors, such as basic fibroblast growth factor, insulin-like growth factors, and transforming growth factor-beta 1, have emerged in recent years as multifunctional molecules that typically play such regulatory roles. Adrenocortical cells are highly responsive to these growth factors, in particular in the regulation of cell growth and differentiated functions, such as steroidogenesis. In addition, growth factor expression in the adrenal cortex has been shown to be regulated by physiological stimulants. The spatial expression, release, and activation of these growth factors may, therefore, locally mediate or amplify the actions of the hypothalamo-pituitary axis and the renin-angiotensin system on adrenocortical proliferation, differentiation, and steroidogenesis.

Induction of steroidogenic enzyme genes by insulin and IGF-I in cultured adult human adrenocortical cells

Insulin and the insulin-like growth factors (IGFs) have multiple role in gene expression in steroidogenic cells. We investigated the regulation of steroidogenic enzyme gene expression by insulin and IGF-I in primary cultures of human adrenocortical cells from donors of ages 19-77 years. The effects of insulin and IGF-I observed here were independent of age and sex of the donor. After 5 days in serum-containing medium, cultures were exposed to insulin or IGF-I together with cyclic AMP analogs or ACTH in serum-free defined medium. Insulin and IGF-I at physiological concentrations increased mRNA levels for 17 alpha-hydroxylase and type II 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in the absence of cyclic AMP or ACTH. They had lesser effects on 21-hydroxylase and cholesterol side-chain cleavage enzyme mRNA levels and were3 without effect on 11 beta-hydroxylase mRNA. All steroidogenic enzyme mRNAs were strongly increased by cyclic AMP or ACTH, and this increase was potentiated by insulin or IGF-I. These effects of insulin and IGF-I were accompanied by decreases in the ratio of dehydroepiandrosterone/cortisol synthesized from pregnenolone by the cultures. Induction of steroidogenic enzyme genes in adult human adrenocortical cells by insulin and IGF-I is unlikely to occur by means of a cyclic AMP-dependent mechanism. These data increase the evidence for an important regulation of steroidogenesis by these hormones.

Role of growth factors in the developmental regulation of the human fetal adrenal cortex

Development of the human fetal adrenals is characterized by rapid growth and high levels of steroidogenic activity during the latter two-thirds of pregnancy. By midgestation, the human fetal adrenals are composed of two distinct cortical zones: the predominant fetal zone, which occupies 80-90% of the cortical volume and produces large amounts of the delta 5-steroid dehydroepiandrosterone sulfate, and the narrow definitive zone, which surrounds the fetal zone. Late in gestation, the peripheral portion of the fetal zone develops into a third, functionally distinct compartment, the transitional zone, which is the likely site of cortisol synthesis. Soon after birth, the adrenal cortex is remodeled and the fetal zone disappears. The adult cortical zones are thought to arise from the definitive zone, which persists postnatally. Development of the human fetal adrenals is regulated primarily by corticortropin (ACTH) secreted from the fetal pituitary. However, as ACTH is not a mitogen per se, its proliferative actions on human fetal adrenal cortical cells are thought to be mediated by autocrine/paracrine growth factors produced by adrenal cortical cells in response to ACTH. In addition, these growth factors appear to modulate the functional response of fetal adrenal cortical cells to ACTH. The roles of several growth factors, including the insulin like growth factors I and II (IGF-I and IGF-II), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), activin, inhibin, and the transforming growth factors alpha and beta (TGF-alpha and TGF-beta) have been examined. In cultured human fetal adrenal cortical cells, EGF, bFGF, and IGF-I and -II are mitogenic, whereas activin and TGF-beta inhibit proliferation. IGF-II, activin, and TGF-beta also modulate ACTH-stimulated steroidogenesis. Human fetal adrenal cortical cells express IGF-II, bFGF and the activin/inhibin subunits, and the abundance of mRNAs for each of these factors is up-regulated by ACTH, suggesting that these growth factors are autocrine/paracrine mediators of ACTH action. Thus, although human adrenal development is primarily regulated by ACTH, its actions appear to be mediated/modulated by a cohort of locally expressed growth factors, the net effect of which results in the unique growth and steroidogenic activity of the human fetal adrenal cortex.

Adrenal incidentalomas: a manifestation of the metabolic syndrome?

Recent evidence suggests that insulin is mitogenic on the adrenal cortex and stimulates adrenocortical tumor formation. We, investigated whether hyperinsulinemia is present in 13 patients with incidentally detected adrenal tumors. Patients with adrenal incidentalomas were obese (mean BMI 29.7 +/- 1.2 kg/m2, normal < 25; % body fat 35 +/- 1.5%, normal < 30%) with increased abdominal fat deposition (waist to hip ratio 0.92 +/- 0.02, normal < 0.85). All 13 patients were insulin resistant. Five had NIDDM, of the remaining patients 5 had fasting insulin concentrations above 15 microE/ml, and all 8 patients had elevated insulin concentrations after 75 g of glucose orally. To further investigate the potential role of insulin we examined its effects on the NCI-h295 cell line. Insulin (1-100 micrograms/ml) stimulated cell proliferation in a time and dose-dependent matter without affecting cortisol synthesis. At this concentrations insulin was equally potent to IGF I (10-80 ng/ml) or IGF II (10-100 ng/ml). We conclude that the majority of patients with adrenal incidentalomas are insulin-resistant/hyperinsulinemic. Insulin stimulates adrenal cancer cell lines in vitro. We propose that adrenal incidentalomas are a newly recognized manifestation of the metabolic syndrome comparable to insulin-mediated stimulation of the ovary in the polycystic ovary syndrome.

Chronic hyperinsulinemia and the adrenal androgen response to acute corticotropin-(1-24) stimulation in hyperandrogenic women

OBJECTIVE

Many women with androgen excess demonstrate elevated circulating insulin levels independent of obesity. In addition, in these women some investigators have demonstrated a negative correlation between the circulating levels of the adrenal androgens, dehydroepiandrosterone or dehydroepiandrosterone sulfate and insulin. The mechanism by which insulin decreases adrenal androgens is unclear. The objective of this study was to determine whether chronic hyperinsulinemia in hyperandrogenic women results in an alteration in the adrenocortical response to corticotropin, resulting in decreased androgen secretion.

STUDY DESIGN

We studied seven hyperandrogenic women with severe chronic hyperinsulinemia and eight hyperandrogenic normoinsulinemic patients. Nine healthy women served as controls for the basal hormonal levels and the response to a 3-hour, 100 gm oral glucose tolerance test. In all subjects insulin and glucose were measured hourly during the oral glucose tolerance test and the baseline sample was assayed for total testosterone, dehydroepiandrosterone sulfate, dehydroepiandrosterone, androstenedione, sex hormone-binding globulin, and free testosterone. In hyperandrogenic women cortisol, dehydroepiandrosterone, and androstenedione were also measured, before and 60 minutes, after acute intravenous administration of 0.25 mg corticotropin (1-24).

RESULTS

There was no difference in the response of cortisol, dehydroepiandrosterone, or androstenedione to corticotropin-(1-24) stimulation between normoinsulinemic and hyperinsulinemic hyperandrogenic patients. As defined, the hyperinsulinemic patients had higher basal and peak insulin levels and areas under the insulin response curve compared with the normoinsulinemic patients or controls. Total testosterone and dehydroepiandrosterone did not differ among study groups. As expected, hyperandrogenic patients demonstrated lower sex hormone-binding globulin activity and higher free testosterone, androstenedione, and dehydroepiandrosterone sulfate basal levels compared with controls.

CONCLUSIONS

The results of this study do not support the hypothesis that chronic hyperinsulinemia in hyperandrogenic patients significantly inhibits the andrenocortical secretion of dehydroepiandrosterone or androstenedione in response to corticotropin stimulation or the basal circulating adrenal androgen levels. Additional studies, including a greater number of patients, may be needed to fully establish these conclusions.

Elevated serum insulin-like growth factor-1 (IGF-1) levels in women with postadolescent acne

The purpose of this study was to measure the serum levels of IGF-1 in women with postadolescent acne compared to normal controls, and evaluate the relationship of these levels to the levels of androgens, in order to investigate the possible role of IGF-1 in the pathogenesis of acne. Eighty-two female patients with acne between 20 and 25 years of age and thirty-one age-matched control women were studied. We measured the serum levels of total testosterone (T), free testosterone (FT), dihydrotestosterone (DHT), dehydroepiandrosterone sulfate (DHEA-S), and insulin-like growth factor-1 (IGF-1). The levels of IGF-1 in patients with acne (1.26 +/- 0.52 U/ml) were significantly (p < 0.001) increased over those of controls (0.96 +/- 0.32 U/ml). Of 82 acne patients, six (7%) had IGF-1 levels which exceeded the normal range, but there were no significant correlations between IGF-1 and T, FT, DHT or DHEA-S levels or between IGF-1 and acne severity. Since the measurement of serum IGF-1 levels is a convenient indicator of GH secretion, the increase of serum IGF-1 levels seen in some acne patients might reflect an increase of GH.

Differential short- and long-term effects of insulin on ANG II action in human adrenal glomerulosa cells

Insulin is known to modulate several functions in bovine adrenal cells, including steroidogenesis and growth. However, the role of insulin in regulating aldosterone synthesis in human adrenal glomerulosa cells has not been studied. In the present studies, we have examined the acute and chronic effects of insulin on angiotensin II (ANG II)-induced aldosterone synthesis in cultured normal and adenomatous human adrenal glomerulosa cells. Short-term insulin treatment (1.5 h) resulted in inhibition of ANG II-induced aldosterone synthesis. In contrast, chronic treatment (30 h) resulted in potentiation of ANG II action. The 12-lipoxygenase pathway of arachidonate metabolism has been shown to play a key role in ANG II-induced aldosterone synthesis. The acute inhibitory effects of insulin were in part mediated by inhibition of the 12-lipoxygenase pathway. The chronic stimulatory effect of insulin seemed to be due at least in part to the upregulation of cytochrome P-450 side-chain cleavage enzyme levels. These findings suggest that insulin has a differential temporal effect on ANG II action and therefore may be an important regulator of ANG II-induced aldosterone synthesis in the adrenal.

The effect of prolactin, human chorionic gonadotropin, insulin and insulin-like growth factor 1 on adrenal steroidogenesis in isolated guinea-pig adrenal cells

The controlling mechanism for adrenal androgen production has not been elucidated. The presence of receptors for prolactin, human chorionic gonadotropin (hCG), insulin and insulin-like growth factor 1 (IGF-1) in the adrenal cortex raises the possibility of their involvement in the control of adrenal steroidogenesis. This study was undertaken to investigate the effects of prolactin, hCG, insulin and IGF-1 in the presence and absence of ACTH on cortisol and androgen production using isolated guinea-pig adrenal cells. hCG 10(-7) and 10(-6) M significantly increased cortisol (P < 0.05) production. hCG 10(-6) M significantly increased androstenedione (A4) (P < 0.05) production. In the presence of ACTH, 10(-12) M, hCG 10(-6) M significantly increased the cortisol (P < 0.01) and A4 (P < 0.01) responses. Although the mean cortisol and A4 response to ACTH 10(-9) M was reduced in the presence of hCG 10(-6) M, this was not statistically significant. Prolactin 10(-8) M increased cortisol (P < 0.01), A4, and dehydroepiandrosterone (P < 0.05) production. In the presence of ACTH 10(-12) M, prolactin 10(-8) M increased the cortisol and A4 (P < 0.05) responses. However, the maximally ACTH-stimulated cortisol and A4 responses were not significantly altered in the presence of prolactin 10(-8) M. Insulin 10(-11)-10(-8) M and IGF-1 10(-10)-10(-7) M resulted in no significant increase in cortisol, A4 or dehydroepiandrosterone production. This study suggests that prolactin and hCG could play a role in modulation of adrenal steroidogenesis, particularly when ACTH levels are low. However, there was no evidence that prolactin or hCG is the specific cortical androgen stimulating hormone.

Biphasic effect of ACTH on growth of rat adrenocortical cells in primary culture

The proliferation rate of differentiating fetal rat adrenocortical cells was studied in primary culture. In this system, stimulation with ACTH induces differentiation of zona glomerulosa-like cortical cells into zona fasciculata-like cells. Incorporation of bromodeoxyuridine (BrdU) was studied immunocytochemically by use of anti-BrdU antibody, and the proliferation rate was counted from the monolayer colonies of adrenocortical cells. After 21 days of cultivation in the absence of ACTH, the proliferation rate of zona glomerulosa-like cells was 10%. The rate slowly declined to 1% at the age of 100 days during continuous cultivation in the absence of ACTH. Stimulation with ACTH induced a strong inhibition in the proliferation rate (down to 2% during the first 24 h). Treatment with ACTH during the following 48 h led to an extremely intense proliferation of adrenocortical cells at a proliferation rate of 25%. Continuous treatment with ACTH up to 100 days led to a persistent growth of adrenocortical cells, and a proliferation rate over 2-fold higher than in control cells cultivated in the absence of ACTH. Thus, ACTH is the principal growth-promoting factor also in vitro, as has been found in in vivo studies. This growth effect is mediated by a biphasic course; at the beginning of differentiation the effect is inhibitory and is followed by a persistent stimulation of the growth of adrenocortical cells.

Effects of insulin-like growth factor I (IGF-I) on enzymatic activity in human adrenocortical cells. Interactions with ACTH

Cells obtained from 6 adult human adrenals or adrenal fragments were cultured in serum-free synthetic medium (McCoy's) in order to study the isolated effects of IGF-I on steroidogenesis and its interactions with ACTH. After addition of peptide, changes in the activities of steroidogenic enzymes were assessed by measuring certain steroids in the spent medium. These included pregnenolone, 17-hydroxypregnenolone (17-OH-Preg), dehydroepiandrosterone (DHA), 17-hydroxyprogesterone (17-OH-P), androstenedione (AD), 11-deoxycortisol and glucocorticoids (chiefly cortisol and its immediate precursors, 11-deoxycortisol and 17-OH-P) and cortisol itself. The steroid responses obtained with repeated doses of IGF-I (40 ng/ml approximately 10(-9) M), added at 0, 48 and 72 h, over 4 days' culture were quite different from those obtained with repeated doses of ACTH (0.25 ng/ml approximately 10(-10) M). All the steroids measured increased with time of culture under the influence of ACTH and, apart from pregnenolone which peaked, tended to reach a plateau. With IGF-I, by contrast, DHA, AD, 11-deoxycortisol and glucocorticoid production increased initially, then decreased progressively, whereas pregnenolone, 17-OH-Preg and 17-OH-P production was either absent or negative. Cumulative steroid production over 4 days reached similar levels in response to a single dose of IGF-I and/or ACTH, with two major exceptions: pregnenolone dropped significantly with IGF-I [46% +/- 6 (SEM) as opposed to 93% +/- 11 with ACTH, P less than 0.005, n = 5], as did 17-OH-P (48% +/- 11 vs 113% +/- 8 with ACTH, P less than 0.001, n = 6). Increased formation of down-stream metabolites (DHA, AD, 11-deoxycortisol and glucocorticoids) would suggest that IGF-I induced stimulation of the 17 alpha-, 21- and 11 beta-hydroxylases. The responses to ACTH stimulation of cells which 4 days previously had been pre-treated with an initial and single dose of IGF-I and/or ACTH emphasized the impact of IGF-I on the 3-hydroxylation steps in cortisol biosynthesis. Compared with ACTH pre-treatment, the effects of which faded in the long term, pre-treatment with IGF-I resulted in a significantly increased steroidogenic response (P between less than 0.05 and less than 0.01). With the single exception of pregnenolone (43% +/- 4.7), production of all the metabolites was amplified: 17-OH-Preg: 348% +/- 88; DHA: 643% +/- 127; 17-OH-P: 193% +/- 36; AD: 725% +/- 200; 11-deoxycortisol: 573% +/- 110; cortisol: 1000%.(ABSTRACT TRUNCATED AT 400 WORDS)

IGF1 and 2 in two models of adrenal growth

Insulin-like growth factors (IGFs) 1 and 2 were measured in the adrenal glands of rats undergoing either compensatory growth following left unilateral adrenalectomy or adrenal regeneration following bilateral adrenal enucleation. In normal rat adrenal gland, the tissue concentration of IGF2 (7.45 +/- 0.99 pg/micrograms protein) wa higher than IGF1 (1.26 +/- 0.23 pg/micrograms protein), both peptides being more abundant in the inner zones of the adrenal gland compared to the capsule-glomerulosa. During compensatory growth of the right adrenal gland, IGF1 and 2 increased significantly compared with control right adrenal glands at 24 h following left unilateral adrenalectomy (P less than 0.001). At 68 h, the increase remained significant for IGF1 (P = 0.012). The two peptides were measured in the regenerating adrenal gland at 7, 14 and 21 days following bilateral enucleation. Whilst there was a trend towards an increase in the IGF1 and 2 content of regenerating adrenal glands, the increase was significant only for IGF2 in the left adrenal gland at 21 days following enucleation. Plasma IGF1 and 2 did not increase compared to controls during the experiments (110.97 +/- 1.95 and 46.33 ng/ml, respectively), suggesting that the changes in tissue IGF reflect increased local production during rapid growth of the adrenal gland.

Autoradiographic localization of insulin-like growth factor I binding sites in the bovine adrenal gland and on cultured bovine adrenal chromaffin cells

Abstract Previous studies have reported the presence of binding sites for insulin-like growth factor I (IGF-I) in membranes prepared from isolated bovine adrenal medullary cells, and IGF-I was found to regulate the secretory function of bovine chromaffin cells. In the present study, binding sites for IGF-I have been localized in sections of bovine adrenal gland and on cultured bovine adrenal medullary cells, using [(125) l][Thr(59)]-IGF-l as the ligand in conjunction with qualitative autoradiographic techniques. Binding sites were present throughout the adrenal gland and were distributed evenly over all cortical cell layers and over both adrenaline and noradrenaline cell types in the medulla. They were also present at lower density over blood vessels and nerve bundles and over the capsule. The binding of radioligand was to a single class of sites with K(d) 0.61 nM, and was completely displaced by excess unlabelled [Thr(59)]-IGF-l and by insulin (Actrapid, K(d) 1.04muM). Binding sites were also identified on single cells in primary monolayer cultures of bovine adrenal medullary cells. More than 96% of the cells possessed binding sites, although only 85% of such cells were chromaffin cells, as previously determined from dopamine beta-hydroxylase immunohistochemical staining. The results suggest that IGF-I may affect the maturation, growth or function not only of adrenal chromaffin cells but also of many others cell types in this tissue.