MODE OF PULSATILE FOLLICLE-STIMULATING-HORMONE SECRETION IN GONADAL HORMONE-SUFFICIENT AND HORMONE-DEFICIENT WOMEN - A CLINICAL RESEARCH-CENTER STUDY

To test the hypothesis that FSH is secreted at least in part within di screte secretory bursts in women and that the characteristics of episo dic FSH secretion are altered within differing gonadal hormone environ ments, we measured FSH by immunoradiometric assay every 10 min for 24 h in premenopausal women during the early follicular (EF), late follic ular (LF), and midluteal (ML) phases of the menstrual cycle and in pos tmenopausal (PM) women (n = 8 in each group). Secretory events were ev aluated using multiparameter deconvolution. FSH was secreted in an epi sodic manner, with the number of secretory bursts (per 24 h; mean +/- SEM) detected in LF (20 +/- 0.79) and PM (20 +/- 0.90) women being gre ater than that in EF (16 +/- 0.88) and ML (14 +/- 0.93) women. FSH sec retory burst mass (milliinternational units per mL) was significantly higher in PM (12 +/- 1.6) than in EF (1.8 +/- 0.21), LF (3.1 +/- 1.3), or ML (0.8 +/- 0.11) women and primarily reflected a relative increas e in the maximal secretory rate rather than increased burst half-durat ion. The estimated half-life (minutes) of endogenous FSH in LF women ( 155 +/-: 18) was shorter than those calculated in EF (251 +/- 24), ML (277 +/- 38), and PM (231 +/- 18) women. Cross-correlation analysis sh owed strongly positive associations between successively paired serum FSH and LH concentrations in all four groups of women. Deconvolution o f simultaneously obtained LH concentration-time series revealed statis tically significant concordance (13-25%) between FSH and LH secretory episodes at a lag time of 0 min in EF, LF, and PM women and when LH se cretory bursts led FSH secretory bursts by 10 min in ML phase women. H owever, as 75-87% of FSH and LH secretory pulses were discordant, we i nfer the operation of distinct control mechanisms in the generation of FSH and LH release episodes. In summary, these results suggest that F SH is secreted within discrete secretory bursts in women, that the mas s and frequency of FSH secretory bursts differ in women exhibiting var ious gonadal hormone environments, and that FSH and LH secretory burst s occur coincidentally at a higher rate than expected on the basis of chance alone, but at such a low overall rate of concordance that disti nct mechanisms probably operate to direct episodic FSH and LH secretor y activity.