Hormonal Dynamics at Midcycle: A Reevaluation*

Abstract

The dynamics of ovarian and pituitary hormone changes during the midcycle period were evaluated. Changes in hormone levels were determined at 2-h intervals for 5 consecutive days during the periovulatory phase of the cycle in five women. During the 50 h preceding the onset of the surge, the rates of increments for estradiol (E2), progesterone (P4), and LH were similar, with doubling times of 57-61 h. The onset of LH and FSH surges was found to occur abruptly (LH doubled within 2 h). They were temporally associated with the attainment of peak E2 levels and occurred 12 h after the initiation of a rapid rise of P4. The mean duration of the surge was 48 h, with a rapidly ascending limb (doubling time, 5.2 h) lasting 14 h accompanied by a rapid decline of E2 and a continued rise of P4. The surge was followed by a peak plateau of gonadotropin levels lasting for 14 h and a transient leveling of P4. The longer descending limb (half-time, 9.6 h), lasting for 20 h, was associated with a second rapid rise of P4, beginning 36 h after surge onset or 12 h before termination of the surge. By using the onset of the LH surge as a reference point, our data provide a relatively precise picture of the hormonal changes preceding the onset of the gonadotropin surge and the temporal relationship between the multiphasic P4 rise and pituitary-ovarian function.

Ovulation, Female Competition, and Product Choice: Hormonal Influences on Consumer Behavior

“…On average, low-fertility testing sessions took place about 8.37 (SD=1.95) days after ovulation. We used this time of the cycle as our comparison because LH and estrogen levels are known to drop to baseline at this point (Lipson and Ellison 1996;Hoff et al 1983). …”

Empty follicle syndrome after GnRHa triggering versus hCG triggering in COS

“…Thus, the LH surge of the natural cycle is characterized by three phases with a total duration of 48 h [13] as compared to the GnRHa induced LH surge, consisting of only two phases with a duration of 28-32 h [12,13]. In contrast, a bolus of 10.000 IU hCG induces a LH-like activity still measurable in serum for 9-10 days due to the long biological half-life of hCG [14,15].…”

Is the lecithin/sphingomyelin ratio outdated?

“…7 1). Furthermore, as recently demonstrated (Hoff et al 1983), the time of LH doubling is <2 h at the time of onset of the LH surge: variation of about 15% in LH SIR values between the two groups would eventually be related to a difference of about 20 min, which is not enough to explain the observed phenomenon.…”