Estradiol Test - This test measures the levels of estradiol in the blood, which is crucial for checking ovarian function and tracking follicular development in fertility treatments. Estradiol is key throughout the menstrual cycle. High levels in women can indicate ovarian hyperfunction or be seen in pregnancy and fertility treatments. Low levels might suggest ovarian issues or problems with the hypothalamus-pituitary axis. In men, high estradiol levels can lead to gynecomastia due to increased conversion of androgens.