Which enzyme is primarily responsible for the conversion of androstenedione to estradiol in the ovaries?

The conversion of androstenedione to estradiol in the ovaries is primarily facilitated by aromatase. This enzyme plays a crucial role in the biosynthesis of estrogens by catalyzing the aromatization of androgens, specifically converting androgens like androstenedione and testosterone into estrogens such as estrone and estradiol. Aromatase specifically introduces an aromatic ring into the steroid structure, which is essential for estrogen activity.

In the context of ovarian function, the expression of aromatase is highest in the granulosa cells of ovarian follicles, where it converts the androgen precursors produced by the theca cells into estrogens. This enzymatic activity is vital for normal follicular development and the regulation of the menstrual cycle, as estrogens have significant effects on tissue in both reproductive and non-reproductive systems.

Understanding the role of aromatase is essential because it highlights the interconnected nature of steroidogenesis and the importance of androgens in the production of estrogens, thereby playing a crucial role in female reproductive endocrinology.