They enlarge in diameter two or more times and become filled with lipid inclusions that give them a yellowish appearance.

The granulosa cells in the corpus luteum develop extensive intracellular smooth endoplasmic reticula that form large amounts of the female sex hormones progesterone and estrogen (more progesterone than estrogen during the luteal phase).

These hormones may then be converted by aromatase in the granulosa cells into estrogens, including estradiol.

The corpus luteum normally grows to about 1.5 centimeters in diameter, reaching this stage of development 7 to 8 days after ovulation.

Then it begins to involute and eventually loses its secretory function and its yellowish, lipid characteristic about 12 days after ovulation, becoming the corpus albicans.