Endocrine Abstracts

Fibroblasts are important regulators of local inflammatory responses. These responses are further regulated by tissue glucocorticoid levels. Other stromal lineage cells, adipocytes and osteoblasts, express 11beta-hydroxysteroid dehydrogenases (11b-HSDs) which interconvert inactive cortisone and active cortisol. These enzymes are important regulators of local glucocorticoid levels and their expression is regulated by proinflammatory cytokines. We therefore examined expression o...

Patients with Cushing's syndrome develop florid, but reversible central obesity. However, circulating cortisol levels are not elevated in simple obesity. Within human adipose tissue, the enzyme 11 beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is highly expressed and converts inactive glucocorticoid, cortisone to active cortisol. Rodents over-expressing 11beta-HSD1 in adipocytes develop central obesity exclusively as a result of increased adipocyte size. Whilst it has ...

5beta-Reductase is a key glucocorticoid metabolising enzyme. In humans, urinary steroid metabolite profiles suggest an inverse relationship between 5beta-reductase and 11beta-hydroxysteroid dehydrogenase (11HSD1) in obesity and congenital deficiency of 11HSDs. Indeed in the obese Zucker rat hepatic 11HSD1 is decreased and 5beta-reductase increased. Here we use animal models with well characterised alterations in 11HSD1 to explore the link between these enzymes.11HSD1 was m...

Oestrogens act via oestrogen receptors (ER) that are expressed in a wide range of tissues including the vasculature, bone and gonads. Two ER genes known as ERalpha and ERbeta have been identified. In the human splice variants of ERbeta have been identified. ERs form both homodimers and heterodimers upon ligand binding. The aim of the present experiments was to study the functional activity of ERbeta1 (wild type) and ERbeta variant (ERbeta2) in single and double transfection as...

11beta-hydroxysteroid dehydrogenase type 1 (11B-HSD1) catalyses the inter-conversion of cortisone and cortisol, and has been implicated in the pathogenesis of a number of disorders including insulin resistance and obesity. The enzyme is a glycosylated membrane-bound protein, located in the lumen of the endoplasmic reticulum (ER) and has proved difficult to purify in an active state. Previously, we reported the successful expression and purification of human 11B-HSD1 from E. co...

The hypothalamo-pituitary-adrenal (HPA) axis is essential component of the physiological stress response. Functional hypoadrenalism is a hypothetical contributor to mortality in the critically ill, though biochemical evidence for this is conflicting. Most studies have shown that 'high' random plasma cortisol in the first 24 hours of illness is associated with a high mortality. However, these data may be confounded by increased severity of illness in high mortality cohorts. Giv...

The adrenal steroid dehydroepiandrosterone (DHEA) is the most prominent circulating steroid in humans and is also a precursor for sex steroids in peripheral tissues. In prostate, DHEA is a substrate for two major metabolic pathways that produce antagonistic sex steroids. In one pathway, DHEA is converted into potent 5alpha-reduced androgens such as 5alpha-dihydrotestoterone (DHT) and thus shares with testicular androgens the control of prostate growth and functions in both nor...

The key enzymes in the terminal stages of human adrenal gland corticosteroid biosynthesis are aldosterone synthase (AS) and 11-beta hydroxylase (11beta-OHase). Their amino acid sequences differ by only 7% but they exhibit markedly different enzymatic activities. AS is expressed solely in the zona glomerulosa and converts 11-deoxycorticosterone (DOC) to aldosterone whereas 11beta-OHase is expressed mainly in the zona fasciculata and produces cortisol from 11-deoxycortisol. The ...

Background: The enzymes 11beta-hydroxylase and aldosterone synthase are key control steps in regulation of cortisol and aldosterone synthesis. We have previously reported that polymorphic variation of the gene encoding aldosterone synthase (CYP11B2) is associated with altered efficiency of 11b-hydroxylation of the precursor of cortisol, deoxycortisol. In order to examine this relationship in greater detail, we have studied the pattern of steroid precursor metabolite excretion ...

The functions of dendritic cells (DCs) are tightly regulated such that protective immune responses are elicited and unwanted immune responses are prevented. 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been identified as a major factor that inhibits the differentiation and maturation of DCs, an effect dependent upon its binding to the nuclear vitamin D receptor (VDR). Physiological control of 1,25(OH)2D3 levels is dependent upon the enzyme 25-hydroxyvitamin-D3-1alpha-hydroxylase...

We(1) and others have established that men with coronary heart disease (CHD) have lower serum testosterone levels than men with normal coronaries. Hypotestosteronaemia is associated with dyslipidaemia, visceral obesity, insulin resistance, hypertension and a prothrombotic state.The aim of this study was to determine the prevalence of hypogonadism in men with CHD proven by either greater than 70 per cent stenosis of one or more epicardial or greater than 50 per cent stenosi...

The central obese phenotype characteristic of Cushing's syndrome emphasises the role of glucocorticoids (GC) in regulating adipose tissue mass and distribution. We have shown that GCs stimulate adipocyte differentiation, but equally inhibit adipose stromal cell (ASC) proliferation. These effects are regulated at a pre-receptor level through 11beta-hydroxysteroid dehydrogenase type 1, but the 'post-receptor' signalling pathways remain unclear. To define novel GC targets in huma...

Cellular sensitivity to circulating glucocorticoids is critical and is principally determined by the level of glucocorticoid receptor (GR). GR expression is most potently regulated by glucocorticoids themselves, although the mechanism is unknown. The rat GR gene encodes at least eleven alternate and untranslated exons 1, eight of which lie in a 3kb CpG island close to exon 2. We have recently shown that individual exons 1 are subject to tissue specific expression and regulatio...

Increased activity of the hypothalamic-pituitary-adrenal (HPA) axis in men of low birthweight may be an important link between early life events and adult metabolic syndrome. In animal models females are more sensitive to HPA axis programming by manipulations in utero, but whether gender influences susceptibility in humans is unknown.We studied 106 women aged 67-78 y, from Hertfordshire UK, in whom birthweight was recorded. None had pituitary or adrenal disease or were rec...

Aldosterone synthase catalyses the synthesis of aldosterone in the adrenal cortex and is encoded by the CYP11B2 gene. Recent studies have shown that CYP11B2 is also expressed in the central nervous system (CNS) but little is known about its regulation. In this study, we have quantitated CYP11B2 expression in the CNS following dietary manipulation of sodium and infusion of angiotensin II.In study 1, 3 groups of male WKY rats (n=6) were fed normal (0.3%), high (3%) or low (0...

Background: Diabetes increases the risk of developing coronary heart disease irrespective of glycaemic control. Cortisol and growth hormone (GH) abnormalities have been found in these patients and have been proposed as possible mechanisms for this increased risk.Regular exercise, through an unknown mechanism, can modify cardiovascular risk and so prevent or delay the progression of coronary heart disease. In this study we assessed whether an exercise program would a...

The pathway from aldosterone to upregulation of renal sodium re-absorption via the amiloride sensitive sodium channel (ENaC) is strongly implicated in blood pressure control and causation of hypertension (HT) in humans. In order to study these processes further an animal model is required to correlate physiological changes as hypertension develops with the molecular pathways underpinning these in kidney. Transgenic studies indicate mouse is an excellent species for modeling th...

Urine 18-hydroxy cortisol ('18OHF') measurements are claimed to have the potential to discriminate between primary hyperaldosteronism due to either Conn's syndrome/adrenal adenoma (increased values) or idiopathic adrenal hyperplasia (normal values), and also to identify cases of glucocorticoid-suppressible hyperaldosteronism ('GSH').We have evaluated three urine 18-OHF methods using a panel of samples from patients with primary hyperaldosteronism [due to either adenoma (N=...

INTRODUCTIONThe plasma concentrations and urinary excretion rates of 18-OH-F and 18-oxo-F are high in Conn's syndrome and glucocorticoid suppressible hyperaldosteronism, reputedly because aldosterone synthase (AS) has abnormal access to cortisol (F). However, both compounds are also excreted in normal subjects. Two enzymes, 11beta-hydroxylase (11OH) and AS, located in the zona fasiculata (ZF) and zona glomerulosa (ZG) respectively, are capable of 18-hydroxylation but only ...

Aldosterone synthase and 11beta-hydroxylase catalyse the final steps of glucocorticoid (corticosterone) and mineralocorticoid (aldosterone) production in the rat adrenal cortex. They are encoded by the CYP11B2 and CYP11B2 genes respectively. Recent studies have shown that CYP11B1 and CYP11B2 are also expressed in the brain, the vascular system and the heart where it has been suggested that aldosterone influences cardiac function and plays a role in cardiac fibrosis. However, i...

Backround: Androgenic anabolic steroids (AAS) are reported to increase cardiovascular risk by causing adverse changes in lipid profiles, impaired glucose tolerance, hyperhomocystinaemia and hypertension. Recent studies have also suggested impaired vascular reactivity in this group.Aim: To assess cardiovascular risk factors and arterial stiffness in AAS using and non-steroid using male bodybuilders and to compare them with healthy controls.Methods: Studies were conducte...

Glucocorticoids regulate transcription of many genes through the binding to the glucocorticoid receptor (GR) however, their intracellular levels are tightly regulated by the microsomal enzyme 11beta-hydroxysteroid dehydrogenase. Two isozymes of this enzyme have been cloned and characterised; 11beta- hydroxysteroid dehydrogenase type 1 (11beta-HSD1) which is mainly expressed in the liver and adipose tissue and 11beta-HSD type 2 expressed in the kidney and placenta. Within 2.5kb...

Background: Cortisol availability to target tissues represents a complex interplay of synthesis, secretion, metabolism and excretion. A number of these processes are regulated by enzymes that are encoded by genes that are key candidates in determining the metabolic and cardiovascular phenotype in man. Measurement of a range of corticosteroid metabolites allows the activity of these enzymes to be inferred. We have studied the pattern of cortisol metabolite excretion in a large ...

Obese humans and rats exhibit altered glucocorticoid metabolism; increased regeneration of glucocorticoid by adipose 11HSD1 and inactivation by hepatic A-ring reductases. The mechanisms remain unclear; candidates include resistance to insulin-mediated regulation, and secondary effects of adipose products eg TNFalpha. To explore temporal associations between changes in glucocorticoid metabolism, insulin resistance and obesity, we examined effects of high-fat feeding in rats.<br...

Aldosterone synthase catalyses the synthesis of the mineralocorticoid aldosterone in the adrenal zona glomerulosa and is encoded by the CYP11B2 gene. Recent studies have shown that CYP11B2 is also expressed in the cardiovascular system. CYP11B2 expression in the adrenal gland is regulated by the renin-angiotensin system and potassium. However, little is known about its expression in other tissues. In this study, we have quantitated CYP11B2 expression in the cardiovascular syst...

The cortisol day curve has been advocated in the assessment of glucocorticoid replacement therapy in adrenal failure but remains controversial.Objective: To determine the validity of this test within our practice.Method: A retrospective analysis using endocrine laboratory dataset.Results: 102 inpatient cortisol day curves from 76 patients were analysed. The serum cortisol was checked at 5 time points (pre and 1 hour post morning dose, before midday dose, pre and po...

Patients with acute intermittent porphyria (AIP) but not those with porphyria cutanea tarda (PCT) have a reported predominance in urine of 5 beta-reduced androgen metabolites over 5 alpha epimers. Steroids of 5 beta- androstane and pregnane types induce delta-aminolevulinic acid (ALA) synthase in chick embryos in vitro, so altered 5-reduction may predispose to attacks. We have comprehensively examined urine androgen and cortisol metabolites by gas-liquid chromatography and uri...

The Androgen Receptor (AR) is a ligand dependent transcription factor that regulates the development and maintenance of the male reproductive system. Previous studies in AIS have demonstrated ligand binding domain mutations resulting in decreased trans-activation activity through reduced N-terminal/C-terminal interaction of the AR, despite unaltered ligand binding ability.We have introduced mutations in the hinge region of the Androgen Receptor (AR) and assessed the effect...

IntroductionChildren with growth hormone (GH) deficiency and primary/secondary hypoadrenalism are susceptible to hypoglycaemia pre-treatment but little is known about insulin sensitivity and hypoglycaemic susceptibility post-diagnosis.Methods12 children (10.1 plus/minus 4.2y; mean plus/minus 1SD) with pituitary hormone deficiency (5 GHD, 7 GH/cortisol insufficient - GHCD) and 7 (8.2 plus/minus 3.8y) with congenital adrenal hyperplasia (CAH) were studied after obtai...

A 42 year old gentleman presented for a second opinion regarding management of Congenital Adrenal Hyperplasia (CAH) of the salt losing variety. The patient had been under long term follow up elsewhere but had discontinued his medication of his own accord 14 months prior to seeking consultation. Examination revealed a heavily pigmented male patient with protuberant belly. He had easily palpable masses in both flanks. An abdominal CT showed bilateral massive adrenal enlargement ...

INTRODUCTION: Hypertension with hypokalaemia suggests primaryaldosteronism, which is confirmed by high plasma aldosterone with low renin concentrations. CT and MRI scans frequently fail to detect small primary aldosteronomas, and may incorrectly identify ' incidentalomas', so adrenal vein sampling is needed.AIM: To review the clincal and biochemical results on 12 patients who had catheter sampling of adrenal and ivc aldosterone(A) and Cortisol (C)with calculation of Aldosteron...

Background: Although androgens are traditionally considered to be pro-atherogenic, there is increasing evidence to suggest an inverse relationship between testosterone and cardiovascular risk. Endothelial dysfunction is an early event in the process of atherogenesis and may occur as a result of vascular oxidative damage. In vivo, human monocytes release reactive oxygen intermediates as part of a normal immune response.Aim: This study assessed the contribution of testostero...

Urinary steroid profiling by capillary gas chromatography is useful for identification of disordered steroid metabolism and, when 24h collections are made, for determination of steroid production rates. We have noted a substantial clinical demand for analysis of random collections, most commonly from children with precocious puberty and a general belief that relating steroid levels to creatinine would offset the disadvantage of a short collection. Given the known circadian var...

For investigation of mild glucocorticoid resistance, dexamethasone may be inappropriate because, unlike cortisol, it crosses the blood-brain barrier and suitably low doses are difficult to titrate. Prednisolone has been proposed as an alternative but assay of cortisol as an endpoint is subject to cross-reaction with prednisolone in most ligand assays. Using capillary gas chromatography, we can distinguish urinary cortisol and prednisolone metabolites. We have compared this app...

Mutations in the HSD11B2 gene explain the syndrome of apparent mineralocorticoid excess (AME), which is characterised by severe hypokalaemic hypertension. Cortisol acts as a mineralocorticoid through failure of its inactivation to cortisone by 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). Patients are diagnosed by a raised THF+allo-THF/THE ratio. To date, approximately 30 mutations have been described in HSD11B2. Recently, three apparently unrelated kindreds with A...

A 22 years old woman presented with a few days history of nausea, vomiting and general lethargy. She was not on any treatment except the oral contraceptive pill (OCP). She was apyrexial, tachycardic at 140/min with a regular pulse and her blood pressure was 110/70. She was not pigmented. Her plasma sodium was 131 mmol/l, with normal potassium, creatinine and urea. Her arterial blood gas analysis showed a pH of 7.22 and bicarbonate of 12mmol/L. Her TFTs showed a thyrotoxic pict...

An 18 year old young man was first seen in the ENT department with bilateral swelling of the supraclavicular fossae. A clinical diagnosis of Cushing's syndrome was made and the patient was referred to the Endocrine team. Examination showed a BP of 150/100 and clinical features of gross Cushing's syndrome. Initial investigations revealed normal electrolytes, fT4 8.7 pmol/L, TSH 0.69 mIU/L and a basal prolactin of 68280 mIU/ml. A 24 hr urinary free cortisol (UFC) was 3860 nmol/L...

Background: The aldosterone to renin ratio (ARR) is a useful screening test for primary aldosteronism. Renin can be measured as activity or concentration; the accuracy of the ARR depends on these measurements and the factors that may affect them. We carried out two studies; the first assessed the correlation between plasma renin concentration (PRC) and renin activity (PRA) and the agreement between them using two anticoagulants (EDTA and lithium heparin). The second evaluated ...

Hormonal activation of the androgen receptor plays a critical role in male fetal sex differentiation.Current hypotheses concerning estrogen/androgen balance and the role of estrogenic environmental contaminants have led us to investigate the capacity for androgenic/antiandrogenic activity in such chemicals. We have previously developed a sensitive in vitro assay using a telomerase-immortalised human cell line capable of detecting putative endocrine disrupting activi...