The relationship of the renin-angiotensin-aldosterone system to plasma gonadotropin, prolactin, and ovarian steroid patterns during the menstrual cycle

Acromegaly and hypertension: prevalence and relationship to the renin-angiotensin-aldosterone system

The prevalence of arterial hypertension was evaluated in a retrospective study of 158 patients with acromegaly, and results were compared to control populations, namely, the Munich Blood Pressure Study (MBPS) and the Framingham Study. The prevalence of hypertension (defined according to WHO criteria) was significantly increased in female patients but not in men; hypertensive acromegalics were older and tended to have higher body weight compared to normotensive patients. Hypertension was not related to serum concentrations of growth hormone. After successful treatment of acromegaly, growth hormone levels and systolic and diastolic blood pressure fell only in female hypertensive acromegalics; this did not occur in normotensives. The rise in plasma renin activity in response to upright posture was diminished in 57.9% of acromegalic patients. The prevalence of low-renin hypertension in our group of patients was 31.6%, which is similar to figures reported for unselected non-acromegalic subjects with essential hypertension. Orthostatic renin activity was weakly and inversely related (r = -0.3) to blood pressure. No relationship between plasma aldosterone concentration and blood pressure could be detected; however, in acromegalic women, aldosterone rose higher after ambulation than in men. In conclusion, hypertension is a common problem in acromegaly and at least in part related to similar risk factors in control populations. The association with abnormalities of the renin-angiotensin-aldosterone system is difficult to interpret and does not offer an explanation for the slight increase in the prevalence of hypertension.

Circadian variations in plasma renin activity, catecholamines and aldosterone during exercise in women

Four women were studied at 0400 h and 1600 h to determine if their hormonal and hemodynamic responses to exercise varied with the circadian cycle. Esophageal temperature was measured during rest and exercise (60% peak VO2; 30 min) in a warm room (Ta = 35 degrees C; PH2O = 1.7 kPa). Venous blood samples were drawn during rest and exercise and hemoglobin concentration (Hb), hematocrit (Hct), plasma osmolality (Posm), plasma protein concentration (Pp), colloid osmotic pressure (COP), plasma renin activity (PRA), cortisol, aldosterone, norepinephrine (NE) and epinephrine (E) were determined. Changes in plasma volume (PV) were estimated from changes in Hb and Hct. The relative hemoconcentration (-11.2%) was similar at 0400 h and 1600 h, but the absolute PV was smaller at 1600 h than at 0400 h (p = 0.03). The responses of Posm, Pp and COP to exercise were unaffected by time of day. Although PRA was not different at the two times of day, PRA was 244% greater during exercise at 1600 h, but only 103% greater during exercise at 0400 h. The normal circadian rhythms in plasma aldosterone (p = 0.043) and plasma cortisol (p = 0.004) were observed. Plasma aldosterone was 57% greater during exercise, while plasma cortisol did not change. The change in E and NE was greater at 0400 h, but this was due to the lower resting values of the catecholamines at 0400 h. These data indicate that time of day generally did not affect the hormonal or hemodynamic responses to exercise, with the exception that PRA was markedly higher during exercise at 1600 h compared to 0400 h.

Plasma volume during heat stress and exercise in women

Five women were studied during exercise and passive heating to determine whether PV dynamics were affected by the menstrual cycle. The exercise bout (80% VO2 peak) on a modified cycle ergometer and the passive heat stress were done in a hot environment (Ta = 50 degrees C, Pw = 1.61 kPa) during the follicular and luteal phase. Esophageal temperature (Tes) was measured continuously. Blood samples were drawn after each 0.2 degree C increase in Tes and VO2 was measured at that time. Initial PV was estimated at rest during the follicular phase. PV changes from rest were calculated at each Tes from Hb and Hct. During passive heating, PV decreased by a mean volume of 156 (+/- 80) ml to 2.83 (+/- 0.09) l in the follicular phase. During the luteal phase, there was a larger volume reduction (300 +/- 100 ml) during passive heating, and the final PV was lower than in the follicular phase and averaged 2.47 +/- 0.18 l. During exercise, PV decreased 463 (+/- 90) ml to 2.50 (+/- 0.11) l in the follicular and 381 (+/- 70) ml to 2.50 (+/- 0.23) l in the luteal phase. These data indicate that there is a menstrual cycle effect on PV dynamics during passive heating such that more fluid is shifted out of the vasculature during the luteal phase. During severe exercise there is a greater fluid loss during the follicular phase, yet the final PV is not different between phases.

Circadian hormone secretory profiles in women with severe premenstrual tension syndrome

The circadian secretory profiles of serum prolactin, growth hormone and cortisol were measured in two women suffering from severe premenstrual tension syndrome and in two asymptomatic control subjects. Subjects and controls were screened and included after a rigorous selection process. Blood samples were obtained every 30 min over a period of 24 h in each woman both on day 9 (follicular phase) and day 26 (luteal phase) of the menstrual cycle. There was no relationship between the hormonal secretory profiles and the premenstrual tension syndrome.

Prolactin secretion in essential hypertension

This study was designed to evaluate prolactin (PRL) secretion in patients with essential hypertension. PRL secretory pattern was assessed by hourly blood sampling between 2200 and 0800 hours. Additional samples were collected at 0810 and 1000 hours (10 and 120 minutes after assumption of upright posture), as well as at 1200, 1400, and 1800 hours under normal simulated activities. No difference could be detected between the two study groups at any of the sampling times, and the number of secretory episodes were similar. Basal plasma renin activity levels were inversely related to simultaneous PRL levels in the hypertensive patients (r= -0.60, p less than 0.05). In the normal subjects mean overnight PRL levels were inversely related (r= -0.78, p less than 0.05) to the overnight urinary Na/K excretion. There was no PRL response to posture in either group. Hypertensive patients had a greater early response to the dopamine antagonist, metoclopramide than did normal subjects. Our data do not support the previously introduced concept of enhanced PRL responses to normal physiologic stimuli in essential hypertensives. However, it appears that dopaminergic control of PRL secretion may be altered in this disease state.

Premenstrual syndrome

The premenstrual syndrome (PMS) is a major clinical entity afflicting a large segment of the female population. Available information are descriptive in nature and the etiology of this syndrome remains unclear. In this review, both biochemical and psychosocial elements of the syndrome have been explored in an effort to redefine the pathophysiology of this seemingly multifactorial psychoneuroendocrine dysfunction. We propose that luteal phase sensitivity to and subsequent withdrawal from the central effects of the neuropeptides beta-endorphin and alpha-melanocyte-stimulating hormone result in a cascade of neuroendocrine changes within the brain-hypothalamus-pituitary complex. Modulation of neurotransmitter function by these peptides may produce alterations in mood and behavior as well as enhance pituitary release of prolactin and vasopressin. Variable gonadal steroid modulation of these responses from subject to subject likely accounts for the heterogeneous clinical manifestations of the PMS.

Effect of ethinyl estradiol on renin activity and on the concentrations of renin substrate and aldosterone in plasma of ovariectomized women

The effect of high doses of ethinyl estradiol (0.4 mg/day) on renin substrate concentration, renin activity and aldosterone concentration in plasma was studied in eight ovariectomized women. Plasma renin substrate (angiotensinogen) increased already within 24--48 h, reaching a maximum on the third to fifth day after starting estrogen treatment. Thereafter, renin substrate concentration remained relatively constant in a range which was fourfold above the baseline levels. The increase of plasma renin activity was less pronounced and showed considerable between-patient variability; this increase was statistically significant only after 48 hours of estrogen intake. A rise in plasma aldosterone concentration was observed in two of four subjects examined. In one patient treated with 5 mg estradiol benzoate intramuscularly, plasma renin activity increased without any measurable change in renin substrate concentration. Only in one subject treated with ethinyl estradiol did plasma renin activity increase before plasma renin substrate concentration; the results presented do not preclude factors other than the stimulation of renin substrate synthesis in the liver from contributing to the activation of the renin-aldosterone axis during treatment with ethinyl estradiol.