PITUITARY-OVARIAN INTERACTIONS DURING FOLLICULAR MATURATION AND OVULATION

During the past decade, research on hypothalamic-pituitary-ovarian rel ationships in ovulation has explored the contributions of ovarian ster oids and other possible ovarian-derived endocrine factors, such as inh ibin, follistatin, and activin. Follistatin and activin probably have a significant intraovarian and intrapituitary function but are not lik ely to have critical endocrine roles during the follicular phase. Stud ies carried out with both recombinant and highly purified forms of fol licle-stimulating hormone in humans and monkeys indicate that this hor mone is the primary stimulant of follicular growth and development. St udies on animals may have led to incorrect emphasis on the local role of estradiol in primate follicular growth. It appears that estradiol i s not a critical folliculotropin in humans, although it may have some important direct effects on the oocyte.