Ovarian follicles produce increased amounts of Oestrogen and inhibin during
**Core Concept**
Ovarian follicular development is regulated by a complex interplay of hormones, growth factors, and inhibitory proteins. The production of estrogen and inhibin by ovarian follicles is a critical aspect of this process, influencing follicular growth and selection.
**Why the Correct Answer is Right**
Estrogen production by ovarian follicles is primarily mediated by the aromatase enzyme, which converts androgens into estrogens. Inhibin, on the other hand, is produced by the granulosa cells of the follicle and inhibits the production of follicle-stimulating hormone (FSH) by the pituitary gland. During the follicular phase of the menstrual cycle, there is an increase in the production of estrogen and inhibin by the growing follicles, leading to a surge in FSH secretion. This, in turn, promotes further follicular growth and selection.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the production of estrogen and inhibin is not primarily associated with the luteal phase, when progesterone production is dominant.
**Option B:** This option is incorrect because the production of estrogen and inhibin is not primarily associated with the menstrual phase, when the body is preparing for a new cycle.
**Option C:** This option is incorrect because the production of estrogen and inhibin is not primarily associated with the menopausal transition, when ovarian follicular activity declines.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the production of estrogen and inhibin by ovarian follicles is a key regulator of follicular growth and selection, influencing the timing and outcome of ovulation.
**Correct Answer:** C. During the late follicular phase.