The female reproductive cycle is influenced by the relationships between several hormones especially FSH, LH, and estrogen (E2). The hypothalamus signals the pituitary to produce FSH which stimulates the recruitment and development of the ovarian follicles. As the follicles grow, they produce estrogen which signals the hypothalamus to regulate the pituitary’s production of FSH.

When viable follicles are not developing, estrogen levels are low and more FSH is produced leading to elevated Day 3 levels. A high FSH level on Day 3 is one indication of reduced ovarian function or impending menopause.

In general, diminished ovarian reserve is indicated by an FSH of >10, a high FSH/LH ratio (>2.5; even in the FSH level is normal), or a high E2 level (>80 pg/ml). An elevated estrogen level like this may also be caused by an ovarian cyst.

In polycystic ovarian disease (PCOS), the LH level is higher than FSH.

Many other hormone levels are evaluated in the infertility workup.

Elevated levels of androgens (male hormones) can cause irregular ovulation and are seen in obese women and those with polycystic ovarian syndrome (PCOS). These women may also exhibit hirsutism (excessive hair) on the chin and lower abdomen.

Thyroid hormone levels also influence fertility. Hypothyroidism (low levels) can cause anovulation and early pregnancy loss. Hyperthyroidism (high levels) is associated with irregular ovulation, fetal abnormalities, and premature labor.

A comprehensive testing of bloodwork on Day 3 of your cycle is recommended every 3 months.

Learn more about Day 3 bloodwork levels.