Studies on ovarian and adrenal studies at different phases of the menstrual cycle. IV. The effect of dexamethasone suppression and subsequent ACTH stimulation at different phases of the menstrual cycle and following the administration of 150 mg of depot-medroxy-progesterone acetate (DMPA)

Progestins used in endocrine therapy and the implications for the biosynthesis and metabolism of endogenous steroid hormones

Steroidogenesis refers to the de novo synthesis of steroid hormones from cholesterol by a number of sequential enzyme catalysed reactions in the adrenal and the gonads. In addition, circulating steroid hormone precursors are further metabolised in selected peripheral tissues. It has been suggested that the biosynthesis of endogenous steroid hormones can be modulated by progestins, used widely by women in female reproductive medicine. However, as a number of structurally diverse progestins with different pharmacological properties are available, it is possible that these synthetic compounds may vary in their effects on steroidogenesis. This review summarises the evidence indicating that progestins influence the biosynthesis of steroid hormones in the adrenal and gonads, as well as the metabolism of these endogenous hormones in the breast, highlighting the limitations to the current knowledge and directions for future research.

Puberty and structural brain development in humans

Adolescence is a transitional period of physical and behavioral development between childhood and adulthood. Puberty is a distinct period of sexual maturation that occurs during adolescence. Since the advent of magnetic resonance imaging (MRI), human studies have largely examined neurodevelopment in the context of age. A breadth of animal findings suggest that sex hormones continue to influence the brain beyond the prenatal period, with both organizational and activational effects occurring during puberty. Given the animal evidence, human MRI research has also set out to determine how puberty may influence otherwise known patterns of age-related neurodevelopment. Here we review structural-based MRI studies and show that pubertal maturation is a key variable to consider in elucidating sex- and individual- based differences in patterns of human brain development. We also highlight the continuing challenges faced, as well as future considerations, for this vital avenue of research.

Sequence of pituitary–adrenal cortical hormone responses to low-dose physostigmine administration in young adult women and men

We previously demonstrated greater HPA axis activation in adult men compared to adult women following low-dose administration of the anticholinesterase inhibitor, physostigmine (PHYSO). Because blood sampling was done infrequently following PHYSO, the rise times of AVP, ACTH1-39, and cortisol could not be determined. In the present study, we determined the sequence of hormone increases by frequent blood sampling following PHYSO. Twelve adult women and 12 adult men underwent three test sessions 5-7 days apart: PHYSO, saline control, and repeat PHYSO. As in the earlier study, PHYSO produced no side effects in half the subjects and mild side effects in the other half, with no significant female-male differences. None of the hormone responses was significantly correlated with the presence or absence of side effects. In both women and men, the AVP increase preceded the ACTH1-39 increase, which in turn preceded the cortisol increase. The AVP and ACTH AUCs were significantly positively correlated in both women and men, supporting AVP as an acute stimulus to ACTH secretion. Also as in the earlier study, the AVP response to PHYSO was more than twice as great in men as in women, but the difference was not statistically significant. We therefore analyzed the results of both studies combined (N=26 women and 26 men). The men had a significantly greater AVP response and a trend toward a greater ACTH1-39 response compared to the women. These findings further support the concept of sexual diergism (functional sex difference) in the influence of CNS cholinergic systems on HPA hormone secretion.

Plasma pregnenolone levels in cynomolgus monkeys following pharmacological challenges of the hypothalamic–pituitary–adrenal axis

Pregnenolone (PREG) is an endogenous neuroactive steroid that is increased in rodent brain and plasma after hypothalamic-pituitary-adrenal (HPA) activation by acute stress or ethanol administration. Plasma levels of PREG metabolites are altered by pharmacological challenges of the HPA axis, however little is known about HPA regulation of PREG levels in monkeys. PREG concentrations were determined by radioimmunoassay in plasma samples from cynomolgus monkeys, following challenge with naloxone (125 and 375 microg/kg), corticotropin-releasing factor (CRF; 1 microg/kg), dexamethasone (130 microg/kg), adrenocorticotropic hormone (ACTH; 10 ng/kg; 4-6 h after 0.5 mg/kg dexamethasone) and ethanol (1.0 and 1.5 g/kg). Naloxone increased PREG levels, while CRF appeared to increase metabolism of PREG to deoxycorticosterone (DOC). ACTH, administered after dexamethasone, reduced PREG levels, despite an increase in plasma cortisol. Ethanol did not alter PREG levels. Changes in PREG levels were correlated with changes in DOC levels after naloxone 125 microg/kg, CRF, ethanol 1.5 g/kg, and dexamethasone challenges. Furthermore, dexamethasone-induced changes in PREG levels were correlated with subsequent alcohol intake. These data suggest that PREG responses to dexamethasone challenge may represent a trait marker of alcohol drinking. The lack of effect of ethanol on PREG levels suggests differential regulation in non-human primates vs. rodents.

Pituitary, ovarian and endometrial effects of progesterone released prematurely during the proliferative phase

The pituitary, ovarian and endometrial effects of premature exposure to progesterone during the proliferative phase were investigated in 18 normally menstruating women. Daily blood samples were drawn during a control cycle and an endometrial biopsy was obtained on cycle day 6 (in 9 subjects) and on cycle day 11 (in 9 subjects), respectively. Daily blood samples were drawn again throughout a treatment cycle, in which a vaginal delivery system releasing progesterone at a constant rate of 1.4 mg/24 h was inserted and left in situ for 96 hours during cycle days 2-6 (9 subjects) and cycle days 7-11 (9 subjects), respectively. On the 6th and 11th cycle day, respectively, the devices were removed and another biopsy specimen was obtained. In all blood samples the levels of immunoreactive lutropin (LH), estradiol (E2), 17-hydroxyprogesterone (17-HO-P), progesterone (P) and 20 alpha-dihydroprogesterone (20 alpha-HO-P) were estimated by radioimmunoassay. Insertion of the devices resulted in a rapid, approximately six-fold increase (from 0.5 to 3.0 nmol/l) in P levels and an approximately three-fold (from 0.5-0.6 to 1.5-2.0 nmol/l) increase in 20 alpha-HO-P levels. A high degree of correlation was found between P and 20 alpha-HO-P levels. No major changes were observed in the profiles and levels of the other hormonal indices studied. However, premature exposure to small amounts of P during cycle days 2-6 resulted in a significant decrease in the ratio of the E2 to LH peaks and exposure during cycle days 7-11 gave rise to a significant increase in the ratio of the length of follicular to luteal phases. Progesterone released during the early proliferative phase (days 2-6) exerted little, if any, effect on the appearance of the endometrium. However, the same dose of P released during the late proliferative phase (days 7-11) significantly diminished the number of glandular mitoses, the height of the glandular epithelium, reduced pseudostratification and the number of plasmolemmal vesicles, but did not induce any subnuclear vacuolation, predecidual reaction or leucocytic infiltration. It is suggested that systematic studies involving the exposure to progestogens in normally menstruating women during cycle days 7 to 11 will provide a reliable and practical method for the comparative assessment of the potency profile of individual progestogens in women.