Influence of thyroid function on the in vivo cortisol in equilibrium cortisone equilibrium in man

Human steroid biosynthesis, metabolism and excretion are differentially reflected by serum and urine steroid metabolomes: A comprehensive review

Advances in technology have allowed for the sensitive, specific, and simultaneous quantitative profiling of steroid precursors, bioactive steroids and inactive metabolites, facilitating comprehensive characterization of the serum and urine steroid metabolomes. The quantification of steroid panels is therefore gaining favor over quantification of single marker metabolites in the clinical and research laboratories. However, although the biochemical pathways for the biosynthesis and metabolism of steroid hormones are now well defined, a gulf still exists between this knowledge and its application to the measured steroid profiles. In this review, we present an overview of steroid hormone biosynthesis and metabolism by the liver and peripheral tissues, specifically highlighting the pathways linking and differentiating the serum and urine steroid metabolomes. A brief overview of the methodology used in steroid profiling is also provided.

Influence of maternal thyroid hormones during gestation on fetal brain development

Thyroid hormones (THs) play an obligatory role in many fundamental processes underlying brain development and maturation. The developing embryo/fetus is dependent on maternal supply of TH. The fetal thyroid gland does not commence TH synthesis until mid gestation, and the adverse consequences of severe maternal TH deficiency on offspring neurodevelopment are well established. Recent evidence suggests that even more moderate forms of maternal thyroid dysfunction, particularly during early gestation, may have a long-lasting influence on child cognitive development and risk of neurodevelopmental disorders. Moreover, these observed alterations appear to be largely irreversible after birth. It is, therefore, important to gain a better understanding of the role of maternal thyroid dysfunction on offspring neurodevelopment in terms of the nature, magnitude, time-specificity, and context-specificity of its effects. With respect to the issue of context specificity, it is possible that maternal stress and stress-related biological processes during pregnancy may modulate maternal thyroid function. The possibility of an interaction between the thyroid and stress systems in the context of fetal brain development has, however, not been addressed to date. We begin this review with a brief overview of TH biology during pregnancy and a summary of the literature on its effect on the developing brain. Next, we consider and discuss whether and how processes related to maternal stress and stress biology may interact with and modify the effects of maternal thyroid function on offspring brain development. We synthesize several research areas and identify important knowledge gaps that may warrant further study. The scientific and public health relevance of this review relates to achieving a better understanding of the timing, mechanisms and contexts of thyroid programing of brain development, with implications for early identification of risk, primary prevention and intervention.

Dysregulation of 11beta-hydroxysteroid dehydrogenases: implications during pregnancy and beyond

Glucococorticoids play a critical role in the developmental programing and fetal growth. Key molecules mediating and regulating tissue-specific glucocorticoid actions are 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 and 2 isozymes, both of which are expressed in the placenta and the fetal membranes. 11beta-HSD1 is implicated in the pathogenesis of metabolic syndrome and its dysregulation has been observed in pregnancy-related complications (pre-eclampsia, intrauterine growth restriction). Interestingly, preliminary clinical data have associated certain 11beta-HSD1 gene polymorphisms with hypertensive disorders in pregnancy, suggesting, if confirmed by further targeted studies, it's potential as a putative prognostic marker. Animal studies and observations in humans have confirmed that 11beta-HSD2 insufficiency is related with pregnancy adversity (pre-eclampsia, intrauterine growth restriction, preterm birth). Importantly, down-regulation or deficiency of placental 11beta-HSD2 is associated with significant restriction in fetal growth and low-birth weight, and unfavorable cardio-metabolic profile in adulthood. The potential association of 11beta-HSD1 tissue-specific dysregulation with gestational diabetes, as well as the plausible utility of 11beta-HSD2, as a biomarker of pregnancy adversity and later life morbidity, are emerging areas of intense scientific interest and future investigation.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

G6PT-H6PDH-11βHSD1 triad in the liver and its implication in the pathomechanism of the metabolic syndrome

The metabolic syndrome, one of the most common clinical conditions in recent times, represents a combination of cardiometabolic risk determinants, including central obesity, glucose intolerance, insulin resistance, dyslipidemia, non-alcoholic fatty liver disease and hypertension. Prevalence of the metabolic syndrome is rapidly increasing worldwide as a consequence of common overnutrition and consequent obesity. Although a unifying picture of the pathomechanism is still missing, the key role of the pre-receptor glucocorticoid activation has emerged recently. Local glucocorticoid activation is catalyzed by a triad composed of glucose-6-phosphate-transporter, hexose-6-phosphate dehydrogenase and 11β-hydroxysteroid dehydrogenase type 1 in the endoplasmic reticulum. The elements of this system can be found in various cell types, including adipocytes and hepatocytes. While the contribution of glucocorticoid activation in adipose tissue to the pathomechanism of the metabolic syndrome has been well established, the relative importance of the hepatic process is less understood. This review summarizes the available data on the role of the hepatic triad and its role in the metabolic syndrome, by confronting experimental findings with clinical observations.

Comprehensive study of urinary cortisol metabolites in hyperthyroid and hypothyroid patients

OBJECTIVE

To further analyse the significance and mutual relationship of thyroid function-linked alterations in cortisol metabolism that have been separately and variously reported.

PATIENTS AND MEASUREMENTS

Twenty-four-hour urine samples from 21 patients with hyperthyroidism (Graves' disease), 16 patients with hypothyroidism (Hashimoto's thyroiditis), 21 healthy age- and sex-matched controls for hyperthyroidism, and 16 healthy age- and sex-matched controls for hypothyroidism were evaluated for 6beta-hydroxycortisol (6beta-OHF), tetrahydrocortisol (THF), tetrahydrocortisone (THE), allo-tetrahydrocortisol (allo-THF), urinary free cortisol (UFF), urinary free cortisone (UFE) and 17-hydroxycorticosteroid (17-OHCS).

RESULTS

Urinary 17-OHCS, THE and allo-THF levels increased considerably in hyperthyroid patients compared to the controls, while UFF and THF showed no difference between the two groups. Urinary 6beta-OHF was significantly lower in the hyperthyroid patients than in the controls. Both the urinary allo-THF + THF/THE and the UFF/UFE ratios were significantly lower in the hyperthyroid patients than in the controls, whereas only the former was significantly higher in the hypothyroid patients than in the controls. The urinary allo-THF/THF ratio was significantly higher in the hyperthyroid patients and significantly lower in the hypothyroid patients than in the controls. In an analysis of pooled subjects including all groups (n = 64), free T4 levels correlated negatively (P < 0.0001) with the urinary allo-THF + THF/THE ratio but not with the UFF/UFE ratio. The serum levels of free T4 correlated positively (P < 0.0001) with the urinary allo-THF/THF ratio.

CONCLUSION

The thyroid hormones seem to affect the total 11beta-HSD activity (allo-THF + THF/THE) more strongly than the renal 11beta-HSD2 activity (UFF/UFE). 5alpha-reductase activity (allo-THF/THF) is also enhanced in hyperthyroidism, while the reduction of urinary 6beta-OHF in hyperthyroidism might be a secondary effect of the altered activity of the total 11beta-HSD and 5alpha-reductase.

Adrenal corticosteroid biosynthesis, metabolism, and action

Adrenal corticosteroids are essential for life, and an appreciation of the mechanisms underpinning their synthesis, secretion, and mode of action in normal physiology is essential if the physician is to diagnose and treat patients who have Cushing's syndromes effectively. In each case, there have been clinically significant advances in the knowledge base over recent years, notably in the understanding of steroidogenesis, cortisol action, and metabolism. This article describes corticosteroid biosynthesis, metabolism, and action.

11beta-hydroxysteroid dehydrogenase type 1: a tissue-specific regulator of glucocorticoid response

11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) interconverts inactive cortisone and active cortisol. Although bidirectional, in vivo it is believed to function as a reductase generating active glucocorticoid at a prereceptor level, enhancing glucocorticoid receptor activation. In this review, we discuss both the genetic and enzymatic characterization of 11beta-HSD1, as well as describing its role in physiology and pathology in a tissue-specific manner. The molecular basis of cortisone reductase deficiency, the putative "11beta-HSD1 knockout state" in humans, has been defined and is caused by intronic mutations in HSD11B1 that decrease gene transcription together with mutations in hexose-6-phosphate dehydrogenase, an endoluminal enzyme that provides reduced nicotinamide-adenine dinucleotide phosphate as cofactor to 11beta-HSD1 to permit reductase activity. We speculate that hexose-6-phosphate dehydrogenase activity and therefore reduced nicotinamide-adenine dinucleotide phosphate supply may be crucial in determining the directionality of 11beta-HSD1 activity. Therapeutic inhibition of 11beta-HSD1 reductase activity in patients with obesity and the metabolic syndrome, as well as in glaucoma and osteoporosis, remains an exciting prospect.

Apparent cortisone reductase deficiency: a rare cause of hyperandrogenemia and hypercortisolism

A 55-year-old woman presented with androgenetic alopecia which had started at age 40. Her clinical history revealed that, unlike her younger sister, she was unable to conceive and was diagnosed as being sterile at age 30. At age 45, 21-hydroxylase deficiency (late-onset CAH) was assumed and glucocorticoid treatment suggested, but not initiated. There was slight hirsutism, but no other sign of virilization. Retesting of plasma steroids revealed elevated 17-OH-progesterone and free testosterone. Treatment with prednisone, cyproterone acetate, and spironolactone was started with significant clinical success. Surprisingly, the analyses of urinary steroid metabolites revealed a pattern that did not support the diagnosis of 21-hydroxylase deficiency (pregnanetriolone absent, pregnanediol, 17-OH-pregnanolone and pregnanetriol not increased). Abdominal CT showed bilateral adrenal hyperplasia and masses in both ovaries. Bilateral adnexectomy was performed, and cystic teratomas were diagnosed. Postoperative urinary steroid analyses showed a decreased tetrahydrocortisol/tetrahydrocortisone ratio (values around 0.08 as compared to age- and sex-matched controls with a ratio of about 0.5-0.8). Plasma cortisol appeared to be repeatedly elevated with exogenous sources excluded. Mass spectrometry showed that, while the tetrahydro metabolites were mainly cortisone-derived, the metabolites not reduced in A ring were mostly cortisol derivatives. This constellation clearly indicates cortisone reductase deficiency, a defect of hepatic 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD1). This enzyme catalyzes the oxidation of cortisol to cortisone and the reduction of cortisone to cortisol. In contrast to the corresponding kidney enzyme (11 beta-HSD2), its primary activity is, however, reductive. Although this is only the fifth reported case of that defect, more attention should be paid to this condition in hyperandrogenic women, even if elevated 17-OH-progesterone and testosterone suggest a more frequent cause.

Growth hormone replacement inhibits renal and hepatic 11 beta-hydroxysteroid dehydrogenases in ACTH-deficient patients

OBJECTIVES

The commonest side-effects of GH replacement therapy relate to sodium retention but its mechanism is unclear. In rats, GH inhibits renal and hepatic 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) activities. In man, this action might impair inactivation of cortisol to cortisone in the distal nephron thereby allowing cortisol to activate mineralocorticoid receptors. In this study, we examined the effects of GH replacement on cortisol metabolism.

DESIGN

A randomized double-blind study comparing 6 months GH replacement with placebo in adults with GH deficiency due to pituitary or hypothalamic disease.

PATIENTS

6 men and 8 women received placebo and 8 men and 9 women received GH.

MEASUREMENTS

Cortisol and its metabolites were measured in overnight urine samples and in a fasting morning plasma sample at baseline and at 6 months.

RESULTS

Five patients withdrew from the study, 4 because of adverse effects of GH. Amongst those who completed the study, the effects of GH on cortisol metabolism differed between patients with and without ACTH deficiency. Amongst those receiving hydrocortisone replacement (n = 18), GH had no effect on plasma cortisol/cortisone ratio, or urine tetrahydrocortisols/tetrahydrocortisone ratio, but produced a substantial reduction in total urinary cortisol metabolites (from 1326 +/- 191 to 777 +/- 229 micrograms/mmol creatinine; P < 0.01) and an increase in urinary free cortisol/cortisone ratio (from 0.88 +/- 0.10 to 2.57 +/- 0.74; P < 0.02). By contrast, GH had none of these effects in patients with normal ACTH secretion. There were no changes in blood pressure or plasma electrolytes, aldosterone, or renin activity with GH, and no changes in any variables with placebo.

CONCLUSIONS

The increase in cortisol/cortisone ratio in urine but not in plasma, and the lack of effect on hepatic cortisol metabolites, suggests that GH inhibits both the conversion of cortisol to cortisone by renal 11 beta-HSD2 and the conversion of cortisone to cortisol by hepatic 11 beta-HSD1. It is unclear why this action of GH only affects patients with ACTH deficiency. The reduction in total cortisol metabolite excretion suggests that GH also affects bioavailability of hydrocortisone tablets. These observations suggest that glucocorticoid replacement therapy may need to be adjusted in hypopituitary patients who are commenced on GH replacement.

Effects of thyroid hormone (thyroxine) and testosterone on hepatic 11beta-hydroxysteroid dehydrogenase mRNA and activity in pubertal hypothyroid male rats

To investigate the effects of thyroid hormone and testosterone on 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), we measured changes in hepatic 11beta-dehydrogenase activity and its mRNA levels in pubertal methimazole (MMI)-induced hypothyroid male rats following treatment with thyroxine ([T4] 50 microg/kg/d) or testosterone (250 microg/d) for 14 days. Hypothyroidism in male rats markedly reduced hepatic 11beta-HSD1 mRNA levels and serum testosterone concentrations (P < .01). Subcutaneous injection of T4 in the hypothyroid rats significantly (P < .01) increased hepatic 11beta-HSD1 mRNA to approximately normal levels and simultaneously increased serum testosterone levels. However, the same daily dose of T4 administered to castrated male hypothyroid rats for 14 days did not elevate hepatic 11beta-HSD1 activity. Treatment with testosterone for 14 days in castrated hypothyroid male rats and rats without gonadectomy significantly (P < .01) increased the enzyme activity without administration of T4. Variations in hepatic 11beta-HSD1 activity were demonstrated to be accompanied by changes in serum testosterone levels in the rats following alteration of the thyroid hormone state. These results suggest that the effect of T4 in increasing the subnormal 11beta-HSD1 gene expression in hypothyroid male rats is mediated by its ability to increase testosterone production in these rats, because in castrated hypothyroid rats, T4 does not elevate 11beta-HSD1 gene expression.

Acute effects of thyroid hormones on the production of adrenal cAMP and corticosterone in male rats

The acute effects of thyroid hormones on glucocorticoid secretion were studied. Venous blood samples were collected from male rats after they received intravenous 3,5,3'-triiodothyronine (T3) or thyroxine (T4). Zona fasciculata-reticularis (ZFR) cells were treated with adrenocorticotropic hormone (ACTH), T3, T4, ACTH plus T3, or ACTH plus T4 at 37 degrees C for 2 h. Corticosterone concentrations in plasma and cell media, and also adenosine 3',5'-cyclic monophosphate (cAMP) production in ZFR cells in the presence of 3-isobutyl-1-methylxanthine, were determined. The effects of thyroid hormones on the activities of steroidogenic enzymes of ZFR cells were measured by the amounts of intermediate steroidal products separated by thin-layer chromatography. Administration of T3 and T4 suppressed the basal and the ACTH-stimulated levels of plasma corticosterone. In ZFR cells, both thyroid hormones inhibited ACTH-stimulated corticosterone secretion, but the basal corticosterone was inhibited only with T3 > 10(-10) M or T4 > 10(-8) M. Likewise, T3 or T4 at 10(-7) M inhibited the basal- and ACTH-stimulated levels of intracellular cAMP. Physiological doses of T3 and T4 decreased the activities of 3 beta-hydroxysteroid dehydrogenase, 21-hydroxylase, and 11 beta-hydroxylase. These results suggest that thyroid hormones counteract ACTH in adrenal steroidogenesis through their inhibition of cAMP production in ZFR cells.

The effect of growth hormone replacement therapy on cortisol-cortisone interconversion in hypopituitary adults: evidence for growth hormone modulation of extrarenal 11 beta-hydroxysteroid dehydrogenase activity

OBJECTIVE

Growth hormone (GH) replacement therapy in hypopituitary adults has been associated with a decreased urinary ratio of 11-hydroxy/11-oxo-cortisol metabolites (CoM). This could result from GH regulation of the activity of hepatic or renal 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD1 and 2), the enzymes responsible for cortisol-cortisone interconversion, or alternatively it might reflect decreased cortisol availability. To elucidate this, we examined the effect of GH on urinary cortisol, cortisone and cortisol metabolites in hypopituitary adults at increasing doses of hydrocortisone replacement.

DESIGN

Patients received increasing twice daily doses of hydrocortisone (HC) (10/10, 20/10, 40/20 mg) each week, before and during 2 months of GH replacement (0.25 U/kg/week).

PATIENTS

Seven hypopituitary adults (three men and four women, age range 47-64 years) with combined GH and ACTH deficiency. Three additional patients with GH deficiency, but intact ACTH reserve, were also studied.

MEASUREMENTS

Urine steroid metabolite profiles were measured in 24-hour urine collections by gas chromatography after each week of treatment. Urinary free cortisol and free cortisone were measured by radioimmunoassay as a measure of renal 11 beta-HSD-2 activity.

RESULTS

Total urinary CoM increased with rising doses of HC, but at each particular HC dose, were unchanged after GH (before versus after GH, median (range): 9.67 (7.86-12.59) versus 9.93 (8.31-14.08); 15.87 (12.37-31.39) versus 17.07 (12.64-23.81); 26.68 (19.07-42.14) versus 26.77 (8.01-37.62) mg/24 hours). The urine ratio 11-hydroxy/11-oxo-CoM decreased significantly with GH treatment, at each HC dose schedule (1.22 (1.02-1.96) versus 0.92 (0.83-1.63) P = 0.018; 1.53 (1.30-2.23) versus 1.23 (0.93-1.46) P = 0.018; 1.87 (1.45-2.70) versus 1.56 (1.22-1.79) P = 0.018). The urinary ratio tetrahydrocortisols/tetrahydrocortisone, an alternative index of 11 beta-HSD activity, also fell with GH therapy at each HC dose (P = 0.049; P = 0.018; P = 0.043). In contrast, the urinary 20-hydroxy/20-oxo-CoM ratio exhibited a small increase with GH, suggesting that the changes observed above were not simply due to changes in redox status. The patients with GH deficiency, but intact ACTH reserve, demonstrated changes in urine steroid profiles similar to the group receiving hydrocortisone replacement. Urinary free cortisone and urinary free cortisol/free cortisone ratios did not change with GH therapy, but the serum cortisol/ cortisone ratio fell significantly with GH therapy at each hydrocortisone dose.

CONCLUSIONS

GH therapy decreases the urinary ratios 11-hydroxy/11-oxo-cortisol metabolites and tetrahydrocortisols/tetrahydrocortisone, but not urinary free cortisone or the urinary free cortisol/free cortisone ratio. This effect is not secondary to reduced cortisol availability. These findings provide further evidence for direct or indirect modulation of cortisol metabolism by growth hormone and suggest that this occurs at hepatic or an alternative site of 11 beta-hydroxysteroid dehydrogenase-1 activity.

Radioimmunoassay of cortisone in serum, urine, and saliva to assess the status of the cortisol–cortisone shuttle

We have developed a new assay for cortisone (E) in serum, saliva, and urine involving Celite® chromatography followed by RIA with 125I-labeled E and scintillation proximity assay. The chromatography step separates cortisol (F) from E, and in combination with their RIAs, permits assessment of the status of the F–E shuttle. We report the results of basal, postcorticotropin (ACTH), and postdexamethasone E and F concentrations and their circadian fluctuations in the serum, saliva, and urine of healthy volunteers. The serum and urine F/E ratios were increased in patients with ectopic ACTH secretion, whereas in adrenal adenoma and Cushing disease only the urinary ratio was increased. In chronic renal insufficiency this ratio was increased in serum (23.5 ± 3.9) but diminished in saliva (0.38 ± 0.11), and in apparent mineralocorticoid excess the ratios were high in serum (44.3 ± 9.3) and urine (5.35 ± 0.85) compared with those of healthy subjects (serum 9.8 ± 3.5, urine 0.52 ± 0.29, saliva 0.52 ± 0.29).

Stress, hormonal changes, alcohol, food constituents and drugs: factors that advance the incidence of tobacco smoke-related cancer?

The genotoxicity of the most potent carcinogen in cigarette smoke [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)] is dependent on the relationship between its activation by cytochrome P450 enzymes and its detoxification by carbonyl reduction to NNK alcohol (NNAL) followed by glucuronidation. Recently, '11 beta-hydroxysteroid dehydrogenase' (11 beta-HSD 1) was identified to be responsible for NNK carbonyl reduction. It is now speculated that differences in tissue expression of 11 beta-HSD 1, as well as genetic polymorphisms, may have profound influences on the organospecificity and potency of NNK-induced cancerogenesis. Moreover, endogenous and exogenous substrates or inhibitors of 11 beta-HSD 1 may shift the NNK/NNAL equilibrium and favour NNK toxification in a variety of physiological and therapeutic situations. These issues are discussed here by Edmund Maser, who also describes how recent observations could provide the experimental base for epidemiological or clinical studies, which focus on polymorphisms in 11 beta-HSD 1 enzyme expression, as well as on implications of exposure to 11 beta-HSD 1 modulators and concurrent smoking.

The integrated concentration of cortisone is reduced in obese children

We evaluated the possibility that there is enhanced conversion of cortisol (F) to cortisone (E) in obese children. IC-E was measured from 15 lean children aged 12.7 +/- 2.2 years, body mass index Z-score (BMI-SD) = -0.35 +/- 0.82, IC-F = 197 +/- 70 nM/l and 9 obese children aged 12.3 +/- 3.2 years, BMI-SD = + 4.7 +/- 2.1, IC-F = 149 +/- 53 nM/l. IC-E was higher in lean children 76 +/- 25 nM/l compared to obese 60 +/- 11 nM/l (p < 0.04). There was no difference in the ratio of IC-E/IC-F between lean 0.40 +/- 0.10 and obese subjects 0.42 +/- 0.09 (p < 0.06). IC-E was directly correlated with IC-F: IC-E = 0.25 x IC-F + 26 (n = 24, r2 = 0.57, p < 0.0001). In a multiple regression model (overall r2 = 0.32, p < 0.02), IC-E was related to BMI-SD inversely (p < 0.0054) and influenced as well by interaction of BMI-SD with sex (p < 0.043), IC-E being lower in boys with increasing body mass. In childhood, obesity is associated with decreased plasma IC-E and IC-F levels, the ratio of IC-E/IC-F is independent of body mass. Reduced IC-E levels in obese children are most likely due to the impact of body mass on IC-F.

Opposite effects of sex steroids on 11 beta-hydroxysteroid dehydrogenase activity in the normal and adrenalectomized rat testis

1. Sex steroids have been shown to regulate the biosynthesis of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD). 2. In vitro studies showed that oestradiol (E2) or testosterone (T) can interfere with the bioassay of enzyme activity, but not progesterone (P4). 3. For in vivo studies, the activity of 11 beta-HSD in the testis of normal and adrenalectomized (ADX) adult male Wistar rats was determined following a daily IM injection of sex steroids for 7 days. 4. The 11 beta-HSD activity was significantly reduced (P < 0.01) either by E2 or T in normal and ADX rats. The enzyme activity in normal rats given both T and E2 was even lower (P < 0.001) than when E2 was given alone. 5. P4 given to normal and ADX rats increased the enzyme activity higher than normal (P < 0.001). 6. The presence of corticosteroids influenced the effects of E2, but not of T and P4, on 11 beta-HSD activity. 7. E2 and T downregulate 11 beta-HSD activity, whereas P4 increased it. E2 did not act through lowering T level.

The effect of growth hormone replacement on cortisol metabolism and glucocorticoid sensitivity in hypopituitary adults

OBJECTIVE

Growth hormone (GH) replacement therapy in hypopituitary adults is associated with sodium and water retention. The underlying mechanisms are incompletely understood and a possible contribution of altered cortisol metabolism or action has not been evaluated. We have investigated the effect of GH replacement therapy on cortisol metabolism, cortisol binding globulin and in-vitro glucocorticoid sensitivity in a group of adult hypopituitary patients.

DESIGN AND PATIENTS

We studied 19 adult hypopituitary patients (18 adult onset, M:F, 6:13), who were receiving conventional hydrocortisone (16 patients), thyroxine (14 patients), triiodothyronine (1 patient), sex steroid (9 patients), human chorionic gonadotrophin (1 patient) or desmopressin (6 patients) replacement during a 6-month, double blind controlled trial of GH therapy (active:placebo, 8:11) followed by a 6-month open phase of GH (mean dose: 0.2 IU/kg/week, range 0.051-0.27) and after a 6-week washout phase following discontinuation of GH therapy.

MEASUREMENTS

Twenty-four-hour urine free cortisol, cortisol metabolites (CoM), ratio 11-hydroxy/11-oxo CoM (F/E) and ratio 5 alpha/beta tetrahydrocortisol were measured at 6 months, 12 months and after the 6 week washout phase. Serum cortisol binding globulin was measured basally, at 6 months, 12 months and after washout. Glucocorticoid sensitivity was determined in lymphocyte preparations from 8 patients, during GH therapy and after washout, using an in-vitro technique dependent on dexamethasone suppression of phytohaemagglutinin-stimulated thymidine incorporation into DNA. Plasma renin activity and aldosterone were measured after 6-12 months GH therapy and after washout.

RESULTS

After 6 months of GH, in patients on hydrocortisone (n = 9), there were significant decreases in CoM (mean decrement 21%, P < 0.01), F/E (mean decreased from 1.27 to 1.0, P = 0.04; reference range 0.33-1.29) and 5 alpha/5 beta tetrahydrocortisol (mean decreased from 0.67 to 0.48, P = 0.01) and a subsequent increase after washout. Patients not on hydrocortisone (n = 2) demonstrated a normal basal F/E falling by 25% on GH therapy but no change in CoM. During 12 months of GH therapy, patients on hydrocortisone (n = 7) demonstrated a further trend to decrement in CoM (P = 0.09) which reversed after washout (P = 0.04). Urine free cortisol tended to fall during GH therapy and increased significantly following washout after 12 months treatment (P < 0.02). Serum cortisol binding globulin decreased by 20% (P < 0.05) during 12 months GH treatment but remained within the reference range. In-vitro studies demonstrated a trend to reduced glucocorticoid sensitivity on GH therapy; the maximum inhibition of phytohaemagglutinin by dexamethasone tended to be less on GH therapy (P = 0.052) and was also lower than in 29 normal volunteers (P < 0.05). There were no significant changes in plasma renin but there was a small increment in aldosterone in recumbent patients (P = 0.04) during the open phase of GH therapy in the placebo arm.

CONCLUSIONS

GH therapy in hypopituitary adults is associated with an apparent reduction in availability of administered hydrocortisone as measured by urine cortisol metabolites and urine free cortisol. This effect is unlikely to be clinically significant except possibly in ACTH deficient subjects on suboptimal hydrocortisone replacement. The changes in F/E suggest that GH may directly or indirectly modulate the activity of 11 beta-hydroxysteroid dehydrogenase. The apparent decrease in glucocorticoid sensitivity during GH therapy, demonstrated in vitro, merits further investigation.

Glucocorticoids regulate hippocampal 11 beta-hydroxysteroid dehydrogenase activity and gene expression in vivo in the rat

Chronic glucocorticoid excess or deficiency is associated with hippocampal dysfunction and neuronal death. 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD), which catalyses the reversible conversion of corticosterone to inactive 11-dehydrocorticosterone, regulates glucocorticoid access to receptors in the kidney and liver in vivo. The enzyme is also present in the hippocampus where it might modulate glucocorticoid action. We examined the effects of corticosteroid manipulations on hippocampal and peripheral 11 beta-OHSD. In the hippocampus, chronic adrenalectomy (10 days) had no effect on 11 beta-OHSD activity, compared to sham-operated controls. Treatment of adrenalectomized animals with dexamethasone (200 micrograms/kg.day-1), but not aldosterone (20 micrograms/kg.day-1), for 10 days significantly increased hippocampal 11 beta-OHSD activity compared with sham or adrenalectomized rats (22% and 23% rise respectively, P < 0.05). These effects reflect changes in transcription of the liver-type 11 beta-OHSD gene, with dexamethasone significantly increasing 11 beta-OHSD mRNA expression in the hippocampus compared with sham or adrenalectomized animals (32% and 70% higher respectively, P < 0.05). In the liver, adrenalectomy significantly reduced 11 beta-OHSD activity (16% lower), which was restored to sham levels by dexamethasone, but not aldosterone. Similar trends were seen in 11 beta-OHSD mRNA expression, although these did not reach significance. None of the manipulations altered 11 beta-OHSD activity or mRNA expression in the kidney. The hippocampal effects of dexamethasone were similar to those of chronic stress (arthritis) which increased 11 beta-OHSD activity (20% rise, P < 0.05), although this was not reflected at the level of mRNA. Thus, hippocampal (and hepatic, but not renal) 11 beta-OHSD appears to be regulated by chronic glucocorticoid manipulations and stress. Hippocampal 11 beta-OHSD may thus ensure optimal long-term corticosterone exposure of glucocorticoid-sensitive neurons.

Organ-specific actions of 11 beta-hydroxysteroid dehydrogenase in humans: implications for the pathophysiology of hypertension

Elucidation of a role for 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) in modulating ligand access to renal mineralocorticoid receptors, together with identification of expression of the enzyme in most mammalian tissues, has raised the possibility (i) that glucocorticoid metabolism might influence corticosteroid receptor activation in other sites which are relevant to blood pressure control (e.g., vascular smooth muscle), and (ii) that abnormal 11 beta-OHSD expression might play a pathogenic role in common forms of hypertension (e.g., essential hypertension and the syndrome of ectopic ACTH secretion). This article reviews data from human experiments which suggest that 11 beta-OHSD has tissue-specific actions which can increase or decrease sensitivity of both mineralocorticoid and glucocorticoid receptors to cortisol, and that assessment of cortisol sensitivity may prove equally important as assessment of cortisol secretion rates in hypertensive patients.

Tissue specific effects of thyroid hormone on 11 beta-hydroxysteroid dehydrogenase gene expression

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) by converting active glucocorticoid to an inactive metabolite confers specificity upon the mineralocorticoid receptor (MR) and regulates ligand access to the glucocorticoid receptor (GR). Factors which influence 11 beta-HSD activity seem likely to be of considerable importance in the modulation of both mineralocorticoid and glucocorticoid hormone action. The administration of tri-iodothyronine (T3) to rats has previously been shown to reduce 11 beta-HSD activity in liver but not in kidney. We have studied the effect of T3 on 11 beta-HSD gene expression in vivo in rat liver, kidney, distal colon and pituitary. In addition the effects of T3 on 11 beta-HSD gene expression in vitro in the rat pituitary GH3 cell line have been studied. T3 administration to normal adult rats (40 micrograms/day, s.c. for 1, 3 and 7 days) resulted in a marked decline in liver and pituitary 11 beta-HSD mRNA levels and activity following 3 and 7 days of treatment. These reduced levels were maintained for 3 days following withdrawal of T3 treatment, but returned to control levels after 7 days. In contrast 11 beta-HSD mRNA and activity in kidney and distal colon were unaffected by T3 treatment at each time point studied. In vitro, levels of 11 beta-HSD mRNA and activity in GH3 cells were unchanged following 8, 24 and 72 h treatment with T3 (10(-8) to 10(-6) M). T3 bio-activity was confirmed by a marked dose-dependent decline in the expression of the T3 and glucocorticoid responsive gene, prolactin. T3 inhibits 11 beta-HSD gene expression in both liver and pituitary at a pre-translational level. This effect is absent in the predominantly mineralocorticoid target tissues, kidney and distal colon, i.e. it is tissue specific and as such is consistent with the existence of multiple differentially regulated isoforms of 11 beta-HSD. The time course of the T3 effect in liver and pituitary in vivo and the lack of any effect in vitro suggests that this action is indirect, and not as a result of interaction between the T3 receptor and the putative thyroid hormone response element on the rat 11 beta-HSD gene.

Assay of human plasma cortisone by liquid chromatography: normal plasma concentrations (between 8 and 10 a.m.) of cortisone and corticosterone

A high-performance liquid chromatographic method using ultraviolet detection to quantitate human plasma concentrations of cortisone simultaneously with cortisol and corticosterone is described. The method is based on the use of an octadecyl silica column (100 mm x 2 mm I.D., 3 microns), an ultraviolet absorbance detector (242 nm) with a 10 mm path length flow-cell, and a mobile phase composed of water-tetrahydrofuran-acetonitrile (82:10:8, v/v) containing 5 ml/l triethylamine and citric acid to adjust the pH of the buffer to 6.5. Flumethasone is used as the internal standard. The detection limit of the method for the three steroids is 300 ng/l using a 1-ml sample. The average inter-assay coefficient of variation for cortisone is 3.3% and the average recovery is 100.8%. Possible interferences from common drugs and endogenous and exogenous steroids in the method have been studied. Plasma concentrations (drawn from 8 to 10 a.m.) of cortisone and corticosterone for 43 normal volunteers have been determined.

Kinetics of cortisol metabolism and excretion. A hypothetic model based on the cumulative urinary radioactivity in eight multiple pituitary deficient patients

A new model is proposed to study the kinetics of [3H]cortisol metabolism by using urinary data only. The model consists of 5 pools, in which changes of the fractions of dose are given by a system of 5 ordinary differential equations. After i.v. administration of [3H]cortisol to 8 multiple pituitary deficient (MPD) patients (group I) the urines from each patient were collected in 9-15 portions during the following 3 days. From the urinary data the rate constants of cortisol metabolism were calculated. A published set of urinary data from patients with a normal cortisol metabolism (group II) was used for comparison. The overall half-life of the label in the circulation was 30 min for both groups; the half-life of the label excretion by both groups was 6 h and the time of maximal activity in the main metabolizing pool was 1.8 h in group I and 1.5 h in group II. The 20% of normal cortisol production rate (CPR) in the 8 MPD patients amounted to 7.2 +/- 1.9 mumol/(m2*d). Therefore, the low CPR but normal rate constants, i.e. a normal metabolic clearance rate of cortisol, in the MPD patients suggest a sensitive adjustment of the cortisol response in the target organs.

A possible defect in the inter-conversion between cortisone and cortisol in prepubertal patients with congenital adrenal hyperplasia receiving cortisone acetate therapy

Oral administration of cortisone acetate is widely used to treat prepubertal patients with congenital adrenal hyperplasia (CAH). However, efficient 'first pass' hepatic conversion of the biologically inactive cortisone (E) to cortisol (F) by the 11-reductase component of the 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) system is required for suppression of the hypothalamic-pituitary-adrenal (HPA) axis. 11-beta-HSD activity can be assessed by measurement of urinary tetrahydroderivatives of E (tetrahydrocortisone, THE) and F (tetrahydrocortisol, THF), formed in separate hepatic compartments by reduction of the A ring. Inadequate HPA axis suppression is frequently encountered in peripubertal CAH patients receiving cortisone acetate therapy. In this paper, we describe THE and THF concentration in 24 h urine samples collected every 3-6 months from 14 prepubertal patients with simple virilizing CAH. The patients had been receiving cortisone acetate and 9 alpha-fluorohydrocortisone since diagnosis and were investigated for 2-4 years during which there was marked intra- and inter-individual variation in the level of suppression. Good and poor control of HPA axis suppression were defined on the basis of a profile of early morning serum 17-hydroxyprogesterone, androstenedione, plasma renin activity and 24 h urinary excretion of pregnanetriol, pregnanetriolone and 5 beta, 17 alpha-hydroxypregnanolone. Serum steroids were measured by RIA and urinary metabolites quantitated as methyloxime-trimethylsilylimidazole derivatives by gas chromatography and GC-mass spectrometry. There were no significant differences in the THE/THF ratio between male (n = 9) and female (n = 5) patients during either good or poor therapeutic control. The data were therefore analyzed without consideration of patient sex. Urinary THE/THF (mean +/- SD) was significantly higher in patients during periods of poor control (6.56 +/- 2.51, P less than 0.001) compared with periods of good control (3.73 +/- 0.96) in the same patients. THE/THF levels were also significantly (P less than 0.001) higher in CAH patients, irrespective of the level of control, than those for the normal subjects (1.79 +/- 0.20). Furthermore, THE excretion was significantly higher during periods of poor control compared with good control at all doses of cortisone acetate administered (10-50 mg/day). There were no significant differences in THF excretion. THE levels also rose significantly (P less than 0.001) in response to increasing total dose during periods of poor control. The increase in THF excretion was slight and significant only at doses greater than 40 mg/day compared with doses less than 15 mg/day.(ABSTRACT TRUNCATED AT 400 WORDS)

Thyroid hormone and glucocorticoid regulation of receptor and target gene mRNAs in pituitary GH3 cells

We have examined the effects of triiodothyronine (T3), in dose-response and time-course studies, on T3 receptor (T3R) alpha and beta and glucocorticoid receptor (GR) mRNAs in rate pituitary GH3 cells, in parallel with T3 actions on expression of the growth hormone (GH) target gene. Modulatory influences of dexamethasone (dex) on T3 action were studied by treatment with dex before and during T3 treatment. T3 treatment (1-100 nM) for 24 h reduced T3R alpha mRNA, while the presence of dex (1 microM) enhanced the T3 effect on T3R alpha mRNA and induced T3 inhibition of T3R beta mRNA. Stimulatory effects of T3 treatment on GH mRNA and release were seen in the face of inhibition of T3R mRNAs; these effects on GH were also enhanced by the presence of dex. T3 treatment for 24 h increased GR mRNA; this effect was inhibited by the presence of dex. We next examined the influence of dex on GR and T3R alpha and beta mRNAs, in parallel with effects of dex on the prolactin (PRL) target gene. Modulatory influences of T3 on dex action were studied by treatment of cells with T3 before and during dex treatment. Treatment with dex (0.1-10 microM) for 24 h reduced GR mRNA, an action enhanced by the presence of T3 (100 nM). Dex treatment resulted in inhibition of PRL mRNA and release despite parallel inhibition of GR mRNA by dex; these effects were enhanced by the presence of T3. In contrast to actions on GR, dex has no effect on T3R mRNAs. These effects of T3 and dex on receptor mRNAs suggest that glucocorticoid modulation of T3 action is not related to direct actions on T3R synthesis. In contrast, the mechanism of T3 modulation of glucocorticoid action may be due in part to alteration of GR mRNA expression. Effects of T3 and dex on target gene expression were observed in the presence of parallel reduction of their respective receptor mRNAs. This provides new evidence that interactions between these hormones are likely to be mediated by mechanisms other than regulation of receptor gene expression.

The cortisol-cortisone shuttle and hypertension

11 beta-OHSD is an enzyme complex consisting of 11 beta-DH, converting cortisol to cortisone in man and an 11-keto-reductase performing the reverse reaction. Congenital deficiency of 11 beta-DH should be considered in any child presenting with mineralocorticoid hypertension and suppression of the renin-angiotensin-aldosterone axis. The keystone to diagnosis is the demonstration of a reduced daily production rate of cortisol and an increase in its plasma half-life. In the majority of cases diagnosis can be made from a urinary steroid metabolite profile indicating a high excretion of cortisol relative to cortisone metabolites. Cortisol is the responsible mineralocorticoid, and as such treatment with the pure glucocorticoid dexamethasone will prevent life-threatening hypokalemia, although additional anti-hypertensive drugs are usually required to control blood pressure. Liquorice and carbenoxolone, for years thought to be direct "agonists" of the mineralocorticoid receptor, in fact cause sodium retention through inhibition of 11 beta-DH. The demonstration of 11 beta-DH activity in the vasculature raises the possibility that it locally modules access of glucocorticoids to mineralocorticoid and possibly glucocorticoid receptors in the vessel wall. It remains possible that subtle alterations of this cortisol-cortisone shuttle are responsible for other forms of hypertension which are currently classified under the umbrella diagnosis of essential hypertension.

Clinical pharmacokinetics of prednisone and prednisolone

The growth of knowledge in the field of the pharmacokinetics of prednisolone/prednisone has been slow for several reasons. First, convenient and specific methods for measuring these steroids only became available with the development of high performance liquid chromatographic methods. Secondly, prednisolone is nonlinearly bound to transcortin and albumin: since the unbound concentrations of prednisolone are biologically relevant, it was necessary to determine the free fraction in each plasma sample. Thirdly, due to the short half-life of prednisolone no steady-state is achieved, and therefore area under the concentration-time curve needed to be determined in all studies. Fourthly, prednisolone and prednisone are interconvertible and prednisolone is given intravenously as an ester prodrug, features which created controversies about the correct interpretation of pharmacokinetic results. Finally, the total body clearances of total and (to a lesser degree) of unbound prednisolone increase with increasing concentrations of prednisolone. Therefore, in order to compare pharmacokinetic results between different subjects, standardised doses had to be administered. The investigations performed so far have revealed that: (1) the dose-dependent pharmacokinetics partly explain the clinical observation that an alternate-day regimen with prednisone yields fewer biological effects; (2) the interconversion of prednisone into prednisolone is not a limiting factor, even in patients with severely impaired liver function; (3) hypoproteinaemia per se does not cause increased unbound concentrations of prednisolone in vivo; (4) patients with liver failure, renal failure or a renal transplant, subjects older than 65 years, women on estrogen-containing oral contraceptive steroids or subjects taking ketoconazole have increased unbound concentrations of prednisolone-whereas hyperthyroid patients, some patients with Crohn's disease, subjects taking microsomal liver enzyme-inducing agents or patients on intravenous prednisolone phthalate (instead of prednisolone phosphate) or on some brands of enteric coated prednisolone tablets have decreased concentrations of prednisolone. The biological relevance of the altered pharmacokinetics is supported in part by altered clinical effects and altered effects on cellular immunofunctions.

5 alpha-reductase activity in polycystic ovary syndrome

11 patients with polycystic ovary syndrome (hirsutism and oligomenorrhoea), but with no deficiency of 21-hydroxylase or 3 beta-hydroxysteroid dehydrogenase, had abnormal cortisol metabolism. The high ratio of 5 alpha to 5 beta cortisol metabolites in the urine is consistent with enhanced activity of 5 alpha-reductase. Urinary total cortisol metabolites were higher in patients than controls. Increased 5 alpha-reductase activity in liver and skin enhances hepatic cortisol metabolism at the expense of androgen excess and may be the underlying abnormality in polycystic ovary syndrome.

Investigation of factors influencing 11 beta-hydroxysteroid dehydrogenase (EC 1.1.1.146) activity in midgestational human fetal lung monolayer and explant cultures

We recently suggested that the 11 beta-hydroxysteroid dehydrogenase (11-HSD) activity in midgestational human fetal lung (HFL) cultures comprised at least two enzymes, one oxidative--associated with epithelial cells, the other reductive--related to fibroblast-like cells. In this study, the effects of various hormones on 11-HSD activity were studied by measuring the interconversion of [3H]cortisol and [14C]cortisone. Human chorionic gonadotrophin, placental medium, and low oxygen concentration increased the conversion of cortisone to cortisol while activity in the reverse direction remained unchanged. No effects were seen when adrenocorticotrophin, prolactin, placental lactogen, estrogens, triiodothyronine or oxytocin were added in physiological amounts.

11 beta-Hydroxysteroid dehydrogenase: fact or fancy?

Previous attempts to explain the diverse behavior of 11 beta-hydroxysteroid dehydrogenase (11-HSD) within and between species have not been successful. We now propose that 11-HSD activity is the resultant of the coordinated interaction of two enzyme types, 11-dehydrogenase and 11-reductase. We have demonstrated their separate existence by physico-chemical and kinetic methods. Based on these findings, two classes of disease in humans that have been recently described can now be characterized as being associated with a deficiency in either 11-dehydrogenase or 11-reductase.