Pregnenolone in Man: Plasma Levels in States of Normal and Abnormal Steroidogenesis¹

Abstract

Using a recently described radioimmunoassay, plasma pregnenolone was measured in subjects with normal and abnormal steroidogenesis. Plasma levels were found to be higher in premenopausal women than men and higher in men than in postmenopausal women. Adrenal suppression decreased plasma pregnenolone in normal subjects and gonadal suppression decreased plasma pregnenolone in premenopausal women and men but not in postmenopausal women. Adrenal plus gonadal suppression reduced plasma pregnenolone levels below the sensitivity of the assay i.e., <0.1 ng/ml. Plasma pregnenolone was similar during the follicular and luteal phases of 4 menstrual cycles. Plasma pregnenolone rose in response to the administration of large doses of ACTH to 5 normal subjects. A diurnal rhythm of plasma pregnenolone was observed only in postmenopausal women and in premenopausal women taking estrogen. This suggests that pregnenolone of ovarian origin may have obscured a diurnal rhythm of adrenal pregnenolone in premenopausal women not taking estrogen.The range of plasma pregnenolone in patients with Cushing's syndrome is similar to that of normal subjects. This observation suggests increased intraadrenal turnover of pregnenolone in these patients since plasma fluorogenic corticosteroids were higher in them than in normal subjects. Patients with primary aldosteronism had plasma pregnenolone levels similar to those of normal subjects. ( / Clin Endocrinol Metab 38: 480,1974) P REGNENOLONE is an important intermediate in gonadal and adrenal steroidogenesis. Recent communications (1,2, 3) have reported basal plasma pregnenolone levels in normal subjects. In addition to control values we have measured plasma pregnenolone levels in normal subjects during adrenal stimulation and adrenal suppression, gonadal suppression and combined adrenal and gonadal suppression. Morning and evening plasma pregnenolone levels in normal subjects have been compared. Plasma pregnenolone has been measured in patients with Cushing's syndrome (both those with adrenal hyperplasia and those with adrenal adenomata) during a control period and following dexamethasone administration. Patients

Adrenocortical Function in Old Age: Response to Acute Adrenocorticotropin Stimulation*

“…Normal values for both P 5 and 17OHP 5 in males and females were in the range of those previously reported (see Results) (12)(13)(14)(15)(16)(17)(18).…”

Endocrine Effects of Vasectomy

“…In the latter two cases, these alterations appeared to be of a gradual nature. Under normal circumstances these steroids are primarily of adrenal origin (Crafts et al, 1968;McKenna & Brown, 1974;Rosenfeld et al, 1971) and it is therefore tempting to suggest that vasectomy is associated with long-term alterations in adrenal secretory activity. On the other hand, such relatively small alterations in blood levels could also be ascribed to a long-term change in adrenal secretion induced by environmental factors, rather than vasectomy.…”

Pregnenolone Functions in Centriole Cohesion during Mitosis

“…The cellular concentration of P5 was sustained through G1/S to G2/M phase (Figure S1A available online; 0-9 hr after release from a double thymidine block), but rapidly declined when the cells exited mitosis ( Figure S1A; 10-12 hr). Mass spectra analysis showed that the cellular concentration of P5 in mitotic HeLa cells was 33 nM ± 4.6 (n = 3), which was much higher than that in serum ($1-3 nM) (McKenna and Brown, 1974;Ojasoo et al, 1993). *p < 0.01, analyzed by t test).…”