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Human Ovarian Follicular Dynamics during Natural Menstrual Cycles and Oral Contraception Cycles

Date

2003-09-01

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

Type

Degree Level

Doctoral

Abstract

The objective of the research comprising this thesis was to characterize ovarian follicular development in healthy women of reproductive age undergoing natural menstrual cycles and oral contraception (OC) cycles. We quantified changes in the numbers and diameters of follicles, detected ovulation and assessed changes in the growth and regression of corpora lutea using high-resolution transvaginal ultrasonography. Changes in follicular and luteal development were then correlated with changes in concentrations of reproductively-active hormones and endometrial growth to provide a comprehensive approach to ovarian and uterine function.We documented, for the first time, that women exhibited waves of antral follicular development during the menstrual cycle. Two and three waves of follicle growth were observed. Major and minor waves of follicle development were characterized. Major waves were those in which a dominant follicle was selected for preferential growth; minor waves were those in which dominance was not manifest. Luteal progesterone production appeared to have a negative effect on the emergence and development of follicle waves in women. The ovarian follicular wave phenomenon has provided a new model for studying the growth and regression of ovarian follicles during the human menstrual cycle. Documentation of ovarian follicular waves in women has implications for the development of new strategies to manipulate ovarian follicular development, in particular hormonal contraceptive regimens and infertility therapies. We further documented that ovarian follicular development occurred during the compliant use of oral contraception. Follicles developed to ostensibly ovulatory diameters and either regressed, ovulated, or formed follicular cysts under the suppressive effects of OC. The majority of follicles that developed during OC use emerged during the hormone-free interval (HFI). We interpreted our findings to mean that ovarian follicular development during OC use was associated with loss of endocrine suppression during the HFI, rather than user non-compliance as previously speculated. The number and maximum diameter of follicles that developed during OC use were greater in women administered OC containing 20 g versus 30--35 g Ethinyl -- Estradiol formulations. Our results provided rationale for a reduction or complete elimination of the HFI in OC regimens, and the judicious use of low EE dose OC regimens (i.e., ? 20 g EE). Ovarian follicular development and circulating concentrations of estradiol and LH were not suppressed effectively when OC use was initiated at mid to late stages of follicle development (i.e., ? 10 mm). Our findings demonstrated that dominant follicles secrete estradiol and become increasingly responsive to LH as they acquire functional dominance after becoming physiologically selected for preferential growth during the follicular phase of the menstrual cycle.

Description

Keywords

Menstrual cycle, Ovaries, Oral contraceptives

Citation

Degree

Doctor of Philosophy (Ph.D.)

Department

Obstetrics and Gynecology

Program

Obstetrics and Gynecology

Citation

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DOI

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