Factors affecting the secretion of 18-hydroxycortisol, a novel steroid of relevance to Conn's syndrome

Regulation of 18-oxocortisol and 18-hydroxycortisol by the renin-angiotensin system and ACTH in man

Based on urinary excretion studies the secretion of the cortisol derivatives, 18-oxocortisol and 18-hydroxycortisol are believed to be regulated by ACTH and to a lesser degree by the renin-angiotensin system. Plasma concentrations of 18-oxocortisol and 18-hydroxycortisol were measured during the simultaneous activation of the renin-angiotensin system and inhibition of ACTH secretion. Five healthy male subjects consuming a sodium diet ad libitum were studied. Blood was drawn at 0800 h after 1 h in the supine position. In the first set of experiments, the subjects remained in the supine position from 0800 to 1000 h with or without the oral administration of 2 mg dexamethasone at 0800 h. In the second set of experiments the subjects were placed in the upright position after drawing the 0800 h sample. The subjects were studied with and without dexamethasone administered at 0800 h. Blood was drawn again at 1000 h. Plasma levels of 18-oxocortisol, 18-hydroxycortisol, ACTH, plasma renin activity (PRA), cortisol, aldosterone and 18-hydroxycorticosterone were measured by radioimmunoassay. None of these parameters changed during the 2 h in the supine position. 18-Oxocortisol, 18-hydroxycortisol, aldosterone, 18-hydroxycorticosterone and PRA increased, but ACTH and cortisol did not change when the subjects were placed in the upright position. After dexamethasone administration, 18-oxocortisol, 18-hydroxycortisol, cortisol, aldosterone and 18-hydroxycorticosterone decreased in the supine position and no increase occurred in 18-oxocortisol, 18-hydroxycortisol and 18-hydroxycorticosterone in the upright position. PRA and aldosterone increased and ACTH and cortisol decreased in these subjects. 18-Oxocortisol and 18-hydroxycortisol were more dependent on ACTH regulation and less on the renin-angiotensin system than aldosterone.

Determination of urinary 18-hydroxycortisol in the diagnosis of primary aldosteronism

Urinary excretion of 18-hydroxycortisol (18-OHF), 18-hydroxycorticosterone (18-OHB) and aldosterone 18-glucuronide (Aldo-18-glu) was measured in 10 patients with primary aldosteronism; 5 with aldosterone-producing adenoma (APA) and 5 with idiopathic hyperaldosteronism (IHA), 10 patients with essential hypertension (EHT) and 11 normotensive subjects. In EHT patients, urinary 18-OHF (172 +/- 15 micrograms/24h) and 18-OHB (3.1 +/- 0.6 micrograms/24h) values were not significantly different from 18-OHF (142 +/- 35 micrograms/24h) and 18-OHB (3.6 +/- 0.5 micrograms/24h) in the controls. Urinary 18-OHF values were significantly higher in APA (640 +/- 213 micrograms/24h) when compared with controls and EHT, whereas 18-OHB (11.3 +/- 1.5 micrograms/24h) values were only slightly elevated. Both 18-OHF and 18-OHB were significantly increased in APA compared with 18-OHF (232 +/- 56 micrograms/24h) and 18-OHB (4.6 +/- 0.3 micrograms/24h) in IHA. The two urinary steroids, especially 18-OHF proved to be a useful marker for the diagnosis of APA, confirming the previous findings. Aldo-18-glu was not significantly different between APA and IHA. In normal subjects when sodium intake was restricted to 48meq/day for four days the urinary 18-OHF was increased two fold to 383 +/- 59 micrograms/24h (p less than 0.01 vs control period) associated with comparable rise in plasma renin activity. This suggests that the biosynthesis of 18-OHF is partly under control of renin-angiotensin axis in normal subjects.

The origin and significance of 18-hydroxycortisol: studies in hyperaldosteronism and in bovine adrenocortical cells in vitro

18-Hydroxycortisol has been suggested as a marker compound for a transitional zone between the adrenocortical zonae glomerulosa and fasciculata. The control of secretion of 18-hydroxycortisol has been compared with those of cortisol and aldosterone in normal subjects and patients with primary hyperaldosteronism. Comparisons were also made in isolated bovine zona glomerulosa and zona fasciculata cell preparations. Although there was considerable cross-contamination between fractions, 18-hydroxycortisol secretion occurred with equal facility in both fractions but depended on the availability of cortisol as substrate. Changes in secretion during stimulation following those of cortisol. It is concluded that, in vivo, 18-hydroxycortisol derives mainly from the zona fasciculata. The relevance of these findings to primary hyperaldosteronism and to the nature of the transition is discussed.

18-oxocortisol: effect of dexamethasone, ACTH and sodium restriction

The urinary excretion of 18-oxocortisol in 37 normal subjects consuming a normal sodium diet was 1.2 +/- 0.9(SD) microgram/24 h. Dexamethasone administration to 5 normal individuals suppressed the excretion of 18-oxocortisol from 1.16 +/- 0.5 micrograms/24 h to 0.6 +/- 0.2 micrograms/24 h. While they still received dexamethasone, ACTH administration raised the 18-oxo-cortisol excretion to 3.82 +/- 1.2 micrograms/24 h. Seven normal subjects were placed on a sodium restricted diet, and the urinary excretion of 18-oxocortisol rose from 1.5 +/- 1.21 micrograms/24 h to 8.54 +/- 5.08 micrograms/24 h and aldosterone from 6.6 +/- 2.0 micrograms/24 h to 39.7 +/- 14.6 micrograms/24 h. Two of the seven individuals showed minimal increases in the excretion of 18-oxocortisol, but in all cases aldosterone increased with sodium restriction. The urinary excretion of 18-oxocortisol correlated significantly with the excretion of aldosterone, 18-hydroxycortisol, cortisol, and 19-nordeoxycorticosterone. These studies indicate that 18-oxocortisol secretion is under ACTH regulation, but since sodium restriction also increases the excretion of 18-oxocortisol, the renin-angiotensin system must also participate in its regulation. However, some individuals do not increase their excretion of 18-oxocortisol with sodium restriction, although aldosterone excretion increases as expected, suggesting that additional factors participate in the regulation of 18-oxocortisol production.

Dexamethasone-suppressible hyperaldosteronism: studies on overproduction of 18-hydroxycortisol in three affected family members

We report a newly diagnosed family in which a father and his two sons were found to be hypertensive and to have the rare familial condition dexamethasone-suppressible hyperaldosteronism (DSH). All three patients became normotensive on dexamethasone treatment alone and have been successfully maintained on low doses of the drug for 6 months since diagnosis. Each of the patients had extremely high plasma and urinary concentrations of the recently discovered steroid 18-hydroxycortisol, which were more than ten times higher than the upper normal limit. Plasma levels were readily suppressed by dexamethasone treatment. The hypothesis that 18-hydroxycortisol might derive from 18-hydroxylation of recirculating cortisol was tested by measuring plasma 18-hydroxycortisol levels during low-dose and high-dose hydrocortisone infusions, in a normal subject and in one of the patients with DSH. During the high-dose infusions (with plasma cortisol levels of 3000-5000 nmol/l) there was net production of 18-hydroxycortisol within 8 h, but this was not observed during the low-dose infusions (plasma cortisol levels 300-400 nmol/l). The origin of 18-hydroxycortisol remains uncertain: these findings do not support the recirculation theory, but lend weight to the alternative hypothesis that 18-hydroxycortisol is produced in transitional adrenocortical tissue. This steroid is of considerable value in the differential diagnosis of primary hyperaldosteronism and may also be important as a marker of transitional adrenal cell function.

Adrenal transitional zone steroids, 18-oxo and 18-hydroxycortisol, useful in the diagnosis of primary aldosteronism, are ACTH-dependent

1. The adrenal cortical 'hybrid' steroids 18-oxocortisol (18-OF) and 18-hydroxycortisol (18-OHF) are elevated in patients with typical angiotensin-unresponsive aldosterone-producing adenoma (AII-unresponsive APA) and fall to normal following surgical removal of the adrenal containing the tumour. Since 18-OF was six times the upper limit of normal pre-operatively, the tumour was the site of overproduction of hybrid steroids. 2. The failure of angiotensin-responsive APA to overproduce the hybrid steroids may be linked to their more 'normal' production of cortisol, which falls significantly on removal of the tumours. 3. Hybrid steroid levels were also normal in patients with idiopathic hyperplasia of the adrenals (IHA) and in low renin essential hypertension. 4. In AII-responsive APA, glucocorticoid-suppressible hyperaldosteronism (GSH) and IHA, the hybrid steroids showed brisk responses to stimulation by ACTH and suppression by dexamethasone of endogenous ACTH. 5. Long-term suppression by dexamethasone of hybrid steroids in GSH is consistent with ACTH dependence, rather than angiotensin dependence. 6. Studies of the regulation of hybrid steroid secretion in various categories of hypertension will further define the biosynthetic distinctiveness which is already useful diagnostically.