Effects of follicular phase exercise on luteinizing hormone pulse characteristics in sedentary eumenorrhoeic women

OBJECTIVE Current studies reveal little regarding the Inception of exercise-induced LH changes during physical training. This study aimed to assess the susceptibility of the hypothalamic–pituitary axis to the acute physical stress of exercise in untrained, physically inactive women. The acute effects of submaximal endurance exercise upon the pulsatile LH secretion in the follicular phase were compared with those accompanying leisurely strolling for a similar time period. SUBJECTS All subjects were eumenorrhoelc, as determined by biphasic temperature patterns, detection of the urinary LH surge, and mid-luteal serum progesterone levels. Subjects were not physically active and had little history of strenuous exercise ( V o 2 max = 38·0 ± 1·8) (mean ± SEM) ml/kg/min). DESIGN All women completed a 13·5-hour pulsatility test which included three consecutive 20-minute runs on a treadmill at 50, 60 and 70% of the subjects’maximum oxygen uptake ( n = 16). Six of these same subjects completed a separate test on another occasion in which one hour of leisurely strolling was substituted for exercise. Blood was sampled every 10 minutes via an indwelling cannula for 4·5 hours before and 8 hours after one hour of exercise and or strolling. MEASUREMENTS A pulse algorithm (Pulsar) was used to quantify LH pulse characteristics. RESULTS Exercise produced no significant effects upon LH pulse frequency or mean serum LH concentration. However, exercise of moderate intensity caused a significant increase in LH pulse amplitude ( P < 0·05). Strolling produced no significant changes in LH secretion. CONCLUSION Acute exercise of moderate intensity in the follicular phase of untrained women is an insufficient stimulus to inhibit the GnRH pulse generator in the post-exercise period, yet may produce a slight stimulatory effect on the amount of LH released per pulsePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73507/1/j.1365-2265.1994.tb02794.x.pd

Maturation of hypothalamic-pituitary-gonadal function in normal human fetuses: circulating levels of gonadotropins, their common a-Subunit and free testosterone, and discrepancy between immunological and biological activities of circulating Follicle-Stimulating Hormone

The recent availability of both cordocentesis, a low risk and effective technique for fetal blood sampling, and ultrasensitive/highly specific two-site immunofluorometric assays (IFMA) for pituitary and chorionic glycoprotein hormone (I-LH, I-FSH, and I-CG) measurement prompted us to study the maturation of hypothalamic-pituitary-gonadal function in 114 normal human fetuses (49 females and 65 males) from IT-40 weeks gestation. The subjects were selected from 216 consecutive cordocenteses carried out for rapid karyotyping and diagnosis of fetal infection or hematological disorders. In addition, FSH bioactivity (B-FSH) was measured by rat Sertoli cell aromatase induction assay, glycoprotein hormone a-subunit (\u3b1-SU) by RIA, and circulating free testosterone (fT) by direct analog technique. No significant cross-reactions were recorded in the different measurement methods. In particular, \u3b1-SU did not interfere in any IFMA, and CG cross-reactivity in LH IFMA was 0.5%. Circulating I-LH, I-FSH, and B-FSH levels at 17-24 weeks gestation were significantly higher in female than in male fetuses (I-LH, 48 \ub14 vs. 6.3 \ub1 0.7 U/L; I-FSH, 35 \ub1 2 vs. 0.7 \ub1 .0.1 U/L; B-FSH, 131 \ub1 17 vs. 43.4 \ub1 5.4 U/L). During the last weeks of gestation, a significant decrease in I-LH and I-FSH levels was seen in both female and male fetuses (I-LH, 0.24 \ub1 0.05 and 1.0 \ub1 0.3 U/L; I-FSH, 0.45 \ub1 0.1 and 0.5 \ub1 0.1 U/L), while serum B-FSH remained elevated, but the previously recorded difference between sexes disappeared (54.3 \ub1 7.2 and 58.7 \ub1 7.3 U/L). Circulating I-CG and \u3b1-SU levels at midgestation were elevated in both female and male fetuses (I-CG, 117 \ub1 29 and 191 \ub1 44 U/L; \u3b1-SU, 143 \ub1 16 and 105 \ub1 9 \u3bcg/L, respectively) and decreased thereafter (I-CG, 42 \ub1 9 and 26 \ub1 6 U/L; \u3b1-SU, 60 \ub1 15 and 37 \ub1 6 \u3bcg/L). Serum fT levels at midgestation were significantly lower in females than in males (4.3 \ub1 0.9 vs. 10.0 \ub1 0.8 pmol/L) and increased until term, when the difference between sexes disappeared (16.2 \ub1 1.8 vs. 17.6 \ub1 1.6 pmol/L). The present data 1) show that a clear sex difference in I-LH, I-FSH, and fT secretion characterizes fetal hypothalamic-pituitary-gonadal maturation at midgestation and that the increase in fT contributes to gonadotropin secretion blockade during the third trimester of pregnancy, 2) confirm that circulating I-CG levels are clearly elevated at midgestation and decrease there-after, 3) show that in fetuses of both sexes, there is an enormous excess of circulating \u3b1-SU, the levels of which are 10- to 15-fold higher than those expected to be secreted along with complete glycoprotein hormones, and 4) demonstrate for the first time that B-FSH levels in both males and females are higher than those of I-FSH. Although the source and biochemistry of this FSH-like material remain to be elucidated, the secretion of FSH molecules with increased bioactivity may assure gonadal maintenance and growth during fetal life