Ovarian function in the latter half of the reproductive lifespan

Abstract

The relationship of age to four aspects of ovarian function was investigated: daily progesterone levels, pulsatile progesterone secretion, foHicular and luteal estradiol levels, and preovulatory estradiol levels. Daily progesterone levels decrease after age 40. Pulsatile progesterone secretion remains approximately stable with age, though older women have somewhat higher late luteal activity. Daily follicular and luteal estradiol levels decrease with advancing age, but preovulatory peak estradiol remains stable. Some of these changes undoubtedly have negative effects on fecundity, such as lower follicular estradiol and average progesterone, via effects on endometrial development and support. But other changes identified, such as stability of preovulatory estradiol levels and thereby presumptive capacity to stimulate a luteinizing hormone (LH) surge despite lower follicular and luteal levels, as well as increased pulsatile progesterone secretion around the time of implantation, appear designed t o conserve and maintain function. Thus, ovarian endocrine function over the course of reproductive life represents a process of change, but not one of generalized functional decline. Rather, aging with respect to ovarian endocrine function may proceed on a track, or on multiple tracks, which are largely separable from the continual depletion of oocyte stores which occurs over the lifetime. c 1996 Wlley-Llss, IncThe ovary is a n organ with two related functions: manufacture, storage, and release of oocytes, and production of reproductive hormones, especially estradiol and progesterone. Oocytes with their enclosing follicles are formed during prenatal life, and a woman's supply of gametes is continuously, indeed exponentially (Block, 1952;Baker, 1963;Richardson et al., 1987), depleted over her lifetime, with ultimate exhaustion or near exhaustion leading to menopause. Ovarian endocrine function is closely tied to the cyclic, monthly process of follicular maturation and ovulation. Yet, as we will show here, hormone production as women age does not follow a trajectory paralleling that of declining gamete supply over the life course, which suggests that endocrine function is not linked to oocyte stores in a simple mechanistic fashion.During the first portion, or follicular phase, of the menstrual cycle, developing follicles secrete increasing amounts of estradiol. After ovulation occurs at about midcycle, the remaining follicular cells form the corpus luteum, which secretes progesterone and estradiol during the latter portion, or luteal phase, of the cycle. Both estradiol and progesterone regulate their own production by exerting negative feedback on the stimulatory hormones of the hypothalamus and pituitary. Follicular estradiol promotes endometrial proliferation and affects the maturation and ultimate fertilizability of the oocyte (Yoshimura and Wallach, 1987;Kreiner et al., 1987; Maslar, 1988;Zelinski-Wooten et al., 1994). As titers become sufficiently high, estradiol ceases to suppress hypothalamic and pituitary act...

Reproductive ecology and the endometrium: Physiology, variation, and new directions

“…Most of the focus on fetal loss centered on maternal age and genetic abnormalities of the conceptus (Weinstein et al, 1990;O'Connor et al, 1998;Holman and Wood, 2001). Holman and Wood (2001) describe a U-shaped distribution of pregnancy loss with age, with risk of pregnancy loss at its lowest around age 20, while ovarian measures of fecundity begin to decline much later (O'Rourke et al, 1996;O'Connor et al, 1998).…”

Symptoms of menopause in relation to the timing of reproductive events and past menstrual experience

“…With advancing age and prior to the cessation of menses, ovarian estrogen levels decline (Korenman et al, 1987;Longcope et al, 1986;O'Rourke et al, 1996;Rannevik et al, 1986). Declining estrogen levels are associated with a number of symptoms, specifically hot flashes, night sweats, and vaginal dryness (Whitehead et al, 1993).…”

Lifespan approach to the study of human biology: An introductory overview

“…For some questions, it is most useful to frame investigations solely within biological ti-ajectories. The investigation of changing ovarian function is a good example of the lifespan perspective combined with evolutionary theory or an ecological approach (Ellison, 1996;O'Rourke, 1996).…”

“…For example, despite the use of distinctive life stages, Merchant and Kurz (1993) demonstrate a lifespan approach in their powerful argument that later maternal mortality could be reduced by treating early anemia, vitamin A deficiencies, and infectious disease. Among the papers in this collection, weight gain with pregnancy is related to fat deposition which may have later health consequences (Scholl et al, 19961; the tempo of childhood growth has a slight influence on the age a t menarche (Khan et al, 1996) and may relate to adult levels of ovarian function (Ellison, 1996); lifetime levels of reproduction influence survivorship (Friedlander, 1996); and the experiences of menstruation are related to symptom experience a t menopause (Leidy, 1996).…”