Regulation of follicle differentiation by gonadotropins and growth factors

The rate of ovulation is determined by, among other things, the availability of small follicles that can be recruited into the follicular hierarchy. A decrease in the rate of lay with, for instance, aging has been attributed to both an increase in the rate of atresia and a decrease in the number of small, growing follicles that provide the pool from which follicles are selected into the final growth phase (the preovulatory hierarchy). Among the most important endocrine, paracrine, and autocrine factors that mediate follicle growth and differentiation are the gonadotropins and growth factors. A better understanding of gonadotropin-growth factor interactions that occur during follicle selection and differentiation should lead to the development of management practices or genetic manipulations (Mendelian or molecular) that will enhance the rate of lay at times during the production cycle when egg production is suboptimal.