A method for the simultaneous determination of the secretion rates of cortisol, 11-desoxycortisol, corticosterone, 11-desoxycorticosterone and aldosterone

ABCC1 modulates negative feedback control of the hypothalamic-pituitary-adrenal axis in vivo in humans

BACKGROUND

Cortisol and corticosterone both circulate in human plasma and, due to differing export by ATP-binding cassette (ABC) transporters, may exert differential cellular effects. ABCB1 (expressed in brain) exports cortisol not corticosterone while ABCC1 (expressed in adipose and skeletal muscle) exports corticosterone not cortisol. We hypothesised that ABCC1 inhibition increases corticosteroid receptor occupancy by corticosterone but not cortisol in humans.

METHODS

A randomised double-blind crossover study was conducted in 14 healthy men comparing placebo and ABCC1 inhibitor probenecid. Blood sampling, including from veins draining adipose and muscle, was undertaken before and after administration of mineralocorticoid receptor antagonist potassium canrenoate and glucocorticoid receptor antagonist mifepristone (RU486).

RESULTS

During placebo, systemic plasma cortisol and corticosterone concentrations increased promptly after canrenoate. Cortisol uptake was detected from adipose but not muscle following canrenoate + RU486. Probenecid significantly increased systemic cortisol concentrations, and tended to increase corticosterone and ACTH concentrations, after combined receptor antagonism but had no effects on net glucocorticoid balance in either adipose or muscle. Using quantitative PCR in brain bank tissue, ABCC1 expression was 5-fold higher in human pituitary than hypothalamus and hippocampus. ABCB1 was more highly expressed in hypothalamus compared to pituitary.

CONCLUSIONS

Although displacement of corticosterone and/or cortisol from receptors in adipose and skeletal muscle could not be measured with sufficient precision to detect effects of probenecid, ABCC1 inhibition induced a greater incremental activation of the hypothalamic-pituitary-adrenal axis after combined receptor blockade, consistent with ABCC1 exporting corticosterone from the pituitary and adding to the evidence that ABC transporters modulate tissue glucocorticoid sensitivity.

Peri-operative steroid management in the paediatric population

BACKGROUND

Patients with adrenal insufficiency are at risk of adrenal crisis, a potentially life-threatening emergency in the peri-operative period due to their attenuated ability to mount a cortisol response. There is a lack of standardization regarding peri-operative stress-dose glucocorticoids in paediatric clinical practice with the absence of agreed protocols. For the individual patient, the risk of adrenal crisis must be weighed against the potential adverse clinical outcomes associated with unnecessary or supra-physiologic glucocorticoid dosing in susceptible patients. Specific clinical concerns in the paediatric population include osteopenia, growth restriction and increased risk of cardiovascular disease in adulthood. This review aimed to identify and evaluate available literature in the field of peri-operative stress-dose glucocorticoids.

METHODS

A comprehensive literature search was conducted to construct a narrative review.

RESULTS

The outcome of this review identified that paediatric patients, unlike adults, do not show a graded response to surgical stress with implications for glucocorticoid stress dose regimens for general anaesthesia and less invasive surgical procedures. The studies highlight a lack of information on physiological steroid responses to stress situations and differences in the approach to glucocorticoid replacement strategies in the paediatric population.

CONCLUSION

The review identified there is a lack of high-quality paediatric-specific studies evaluating appropriate stress-dose glucocorticoid regimens in paediatric patients with or at risk of adrenal insufficiency. Further research is needed to establish clear evidence-based clinical guidelines for paediatric peri-operative practice regarding steroid stress dosing in adrenal insufficiency. Current knowledge would suggest that a balanced view of risks and benefits should be taken appropriate to the clinical context, to dictate peri-operative stress-dose glucocorticoids use that permits safe perioperative management.

Glucocorticoids and gut bacteria: "The GALF Hypothesis" in the metagenomic era

A new concept is emerging in biomedical sciences: the gut microbiota is a virtual 'organ' with endocrine function. Here, we explore the literature pertaining to the role of gut microbial metabolism of endogenous adrenocorticosteroids as a contributing factor in the etiology of essential hypertension. A body of literature demonstrates that bacterial products of glucocorticoid metabolism are absorbed into the portal circulation, and pass through the kidney before excretion into urine. Apparent mineralocorticoid excess (AME) syndrome patients were found to have congenital mutations resulting in non-functional renal 11β-hydroxysteroid dehydrogenase-2 (11β-HSD2) and severe hypertension often lethal in childhood. 11β-HSD2 acts as a "guardian" enzyme protecting the mineralocorticoid receptor from excess cortisol, preventing sodium and water retention in the normotensive state. Licorice root, whose active ingredient, glycerrhetinic acid (GA), inhibits renal 11β-HSD2, and thereby causes hypertension in some individuals. Bacterially derived glucocorticoid metabolites may cause hypertension in some patients by a similar mechanism. Parallel observations in gut microbiology coupled with screening of endogenous steroids as inhibitors of 11β-HSD2 have implicated particular gut bacteria in essential hypertension through the production of glycerrhetinic acid-like factors (GALFs). A protective role of GALFs produced by gut bacteria in the etiology of colorectal cancer is also explored.

Why do humans have two glucocorticoids: A question of intestinal fortitude

The main purpose of this review article is threefold (a) to try to address the question "why are two adrenal glucocorticoids, cortisol and corticosterone, secreted by humans and other mammalian species?", (b) to outline a hypothesis that under certain physiological conditions, corticosterone has additional biochemical functions over and above those of cortisol, and (c) to emphasize the role of gastrointestinal bacteria in chemically transforming corticosterone into metabolites and that these re-cycled metabolites can be reabsorbed from the enterohepatic circuit. Cortisol and its metabolites are not secreted into the bile and thus are excluded from the enterohepatic circuit. Corticosterone was the first steroid hormone isolated from adrenal gland extracts. Many believe that corticosterone functions identically to cortisol. Yet, corticosterone causes significant sodium retention and potassium secretion in Addisonian patients, unlike cortisol. In humans, corticosterone and its metabolite, 3α,5α-TH-corticosterone, are excreted via the bile in humans where they are transformed in the intestine by anaerobic bacteria into 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones. These metabolites inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase, being many-fold more potent than 3α,5α-TH-cortisol. Corticosterone has significantly lower Km's for both 11β-HSD2 and 11β-HSD1 enzymatic dehydrogenase activity, compared to cortisol. Patients diagnosed with 17α-hydroxylase deficiency have elevated blood pressure and high levels of circulating corticosterone, 3α,5α-TH-corticosterone, and their 21-dehydroxlated corticosterone derivatives. In humans, these 5α-corticosterone metabolites are likely to influence blood pressure regulation and Na(+) retention by inhibiting the rate of deactivation of cortisol by 11β-HSD isoforms.

An alternative explanation of hypertension associated with 17α-hydroxylase deficiency syndrome

The syndrome of 17α-hydroxylase deficiency is due to the inability to synthesize cortisol and is associated with enhanced secretion of both corticosterone and 11-deoxy-corticosterone (DOC). In humans, corticosterone and its 5α-Ring A-reduced metabolites are excreted via the bile into the intestine and transformed by anaerobic bacteria to 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones (potent inhibitors of 11β-HSD2 and 11β-HSD1 dehydrogenase). Neomycin blocks the formation of these steroid metabolites and can blunt the hypertension in rats induced by either ACTH or corticosterone. 3α,5α-Tetrahydro-corticosterone, 11β-hydroxy-progesterone, and 3α,5α-tetrahydro-11β-hydroxy-progesterone strongly inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity; all these compounds are hypertensinogenic when infused in adrenally intact rats. Urine obtained from a patient with 17α-hydroxylase deficiency demonstrated markedly elevated levels of endogenous glycyrrhetinic acid-like factors (GALFs) that inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity (>300 times greater, and >400 times greater, respectively, than those in normotensive controls). Thus, in addition to DOC, corticosterone and its 5α-pathway products as well as the 11-oxygenated progesterone derivatives may play a previously unrecognized role in the increased Na(+) retention and BP associated with patients with 17α-hydroxylase deficiency.

Cortisol response to operative stress with anesthesia in healthy children

BACKGROUND

Supraphysiological "stress dosing" is generally given to adrenally insufficient patients undergoing operative procedures and/or general anesthesia. However, the normal responses of cortisol to surgery are poorly documented, especially in small children. Recent studies in adults suggest that massive glucocorticoid dosing is not needed, especially in minimally invasive surgery.

OBJECTIVE

We sought to characterize the normal cortisol secretion rate in healthy children undergoing minimally and moderately invasive urological procedures.

DESIGN AND SETTING

This was a prospective observational study conducted at a tertiary referral center.

PATIENTS

Thirty healthy children, ages 5 months to 6 years, were studied undergoing elective urological procedures.

METHODS

Procedures were performed by a single surgeon; anesthesia was by a standard protocol. Sera were obtained at 5 points: iv catheter placement, intubation, 50% completion of surgery, anesthesia reversal, and 1 hour postoperative. Cortisol and cortisone were quantitated by liquid chromatography-tandem mass spectrometry.

RESULTS

Group mean cortisol values ranged from 4.21 to 5.71 μg/dL across the 5 time points; none of these mean values differed significantly (P < .05). There were no differences according to age, time of procedure, caudal anesthesia, and moderate vs minimally invasive procedures; 3 patients had higher values. There was a modest diminution in cortisone across the 5 time points.

CONCLUSIONS

Minimal and moderately invasive urological procedures do not result in a cortisol stress response in healthy children. Peak cortisol levels were seen 1 hour postoperatively. These data suggest that current guidelines for stress dosing in adrenally insufficient patients substantially exceed physiological requirements during minimally invasive procedures.

Gas chromatographic-mass spectrometric method for measuring stable isotope enrichments of underivatized cortisol from small plasma volumes

Isotope dilution methods utilizing quantification of stable enrichment by mass spectrometry has been used recently to determine cortisol production rates in humans. Studies of steroid production and utilization rates require frequent blood sampling, and while stable isotopes are safe for pediatric and perinatal use, the required blood volumes may be problematic using published methodologies. We have developed methods to isolate and quantify the plasma enrichment of cortisol with its stable isotope, [9,12,12-2H3]cortisol using a simple four-step isolation procedure and gas chromatography-mass spectrometry. Isolation is semi-quantitative, but reproducible (mean recovery; 51.5 +/- 5.4% coefficient of variation) and the method does not require derivation. In human studies, this method can determine plasma enrichments between 1 and 10 mol% at plasma concentrations of 2 micrograms/dl or more; only 1 ml of plasma is required. The concentrations of labelled cortisol added to plasma are low (0.2-0.5 micrograms/dl) and are not expected to interfere with the sensitive hypothalamic-pituitary-adrenal feedback system. We conclude that reproducible quantification of stable cortisol isotope enrichment can be achieved from small plasma volumes.

Cortisol production rates measured by liquid chromatography/mass spectrometry

Cortisol production rates (FPRs) in physiologic and pathologic states in humans have been investigated over the past 30 years. However, there has been conflicting evidence concerning the validity of the currently accepted value of FPRs in humans (12 to 15 mg/m2/d) as determined by radiotracer methodology. The present study reviews previous methods proposed for the measurement of FPRs in humans and discusses the applications of the first method for the direct determination of 24-hour plasma FPRs during continuous administration of a stable isotope, using a thermospray high-pressure liquid chromatography-mass spectrometry technique. The technique is fast, sensitive, and, unlike gas chromatography-mass spectrometry methods, does not require derivatization, allowing on-line detection and quantification of plasma cortisol after a simple extraction procedure. The results of determination of plasma FPRs by stable tracer/mass spectrometry are directly in units of mass/time and, unlike radiotracer methods, are independent of any determination of volume of distribution or cortisol concentration. Our methodology offers distinct advantages over radiotracer techniques in simplicity and reliability since only single measurements of isotope ratios are required. The technique was validated in adrenalectomized patients. Circadian variations in daily FRPs were observed in normal volunteers, and, to date, results suggest a lower FRP in normal children and adults than previously believed.

Prevalence, pathogenesis, and functional significance of aldosterone deficiency in hyperkalemic patients with chronic renal insufficiency

Our findings indicate that hypoaldosteronism occurs commonly (23/31 patients) in hyperkalemic patients with chronic renal insufficiency and that the deficiency of aldosterone contributes to the pathogenesis of the hyperkalemia. In most patients (83%), hypoaldosteronism could be accounted for by deficient renal secretion of renin, but in some patients (17%) overt renin deficiency did not appear to be present, and therefore other (unidentified) causes of aldosterone deficiency must be invoked. The results also indicate that the urinary excretion rate of aldosterone secretion rate in this group of patients.

Male pseudohermaphroditism due to 17 alpha-hydroxylase deficiency

This is the first report of a male with 17alpha-hydroxylase deficiency resulting in male pseudohermaphroditism, ambiguous external genitalia, absence of male secondary sexual characteristics, and gynecomastia at puberty. Diagnosis was based on extensive studies of steroid metabolism including the following: low urinary excretion of 17-ketosteroids and 17-hydroxycorticoids which did not increase after ACTH; no response of very low plasma testosterone and dehydroepiandrosterone to adrenocorticotropin (ACTH) or chorionic gonadotropin; and low urinary aldosterone and plasma renin which increased after dexamethasone. Secretion rates of 17-hydroxylated steroids, cortisol (F) and 11-desoxycortisol (S), were very low while desoxycorticosterone (DOC) and corticosterone (B) secretion rates were increased sevenfold. Results expressed as milligrams per meter squared per day were as follows: F, 1.3; S, 0.023; DOC, 0.35; and B, 16 (mean normal values were F, 7.5; S, 0.26; DOC, 0.055, and B, 2.2). Plasma gonadotropins were markedly increased (FSH, 106; LH, 364 mIU/ml). Testicular biopsies revealed interstitial-cell hyperplasia and early spermatogenesis. Karyotype was 46/XY. Pedigree showed no other affected member. At laparotomy ovaries, uterus, and fallopian tubes were absent, vas deferens was incomplete, and prostate was present. External genitalia consisted of small phallus, bifid scrotum, third-degree hypospadias, and small vagina. At puberty there was no growth of body hair or phallic enlargement. Biopsy of marked gynecomastia showed both ducts and acini. Testosterone administration produced virilization. Sexual ambiguity demonstrates strong dependence of external genitalia on androgens for male differentiation. Suppression of Müllerian structures occurred despite female levels of testosterone indicating this step in male differentiation is not testosterone dependent. Pubertal breast development in this male supports the concept of femaleness during ontogeny unless counteracted by male factors. Diagnosis of other adrenocortical enzymatic deficiencies is excluded by the steroidal studies. The clinical response to testosterone excludes testicular feminization. Deficiency of 17-hydroxylation must be added to the cause of male pseudohermaphroditism.