Reproductive health overview

Hypothalamus–Pituitary–Ovarian (HPO) Axis

controls the menstrual cycle, ovulation, and production of estrogen and progesterone

how HPO axis works

1. Hypothalamus: Releases GnRH (gonadotropin-releasing hormone).

2. Anterior pituitary gland: GnRH stimulates the release of two hormones: FSH and LH

3. Ovaries: Produce estrogen and progesterone, which regulate the menstrual cycle and prepare the uterus for pregnancy.

4. Negative feedback: Estrogen and progesterone generally signal the hypothalamus and pituitary to reduce GnRH, FSH, and LH release.

FSH

Stimulates ovarian follicle development and estrogen production

LH

Triggers ovulation and supports progesterone production by the corpus luteum

menstrual cycle

controlled by four hormones: FSH, LH, estrogen, and progesterone

Follicular Phase (Days 1–13)

FSH stimulates follicle growth, increasing estrogen production. Estrogen thickens the uterine lining and eventually triggers an LH surge through positive feedback, leading to ovulation

Ovulation (Around Day 14)

LH surges dramatically, triggering release of the egg from the ovary.

FSH also increases slightly, Estrogen briefly decreases after its preovulatory peak

Luteal Phase (Days 15–28)

ruptured follicle forms the corpus luteum, which produces progesterone and estrogen to maintain the uterine lining for implantation. If pregnancy doesn't occur, the corpus luteum breaks down, causing hormone levels to decrease

Menstruation (Beginning of the Next Cycle)

Falling estrogen and progesterone cause the uterine lining to shed, menstrual bleeding begins, marking Day 1 of a new cycle

Menopause occurs

when the ovaries stop releasing eggs and produce significantly less estrogen and progesterone

Menopause

↓ Estrogen & Progesterone → ↓ Negative Feedback → ↑ GnRH, FSH, and LH

contraindications of estrogen-containing products

Angioedema to estrogen
Abnormal genital bleeding of unknown
origin

Active or current history of DVT (Deep Vein Thrombosis) or PE (Pulmonary Embolism)
Active of current history of thromboembolic disease (stroke, MI)
Known, suspected, or history of breast
cancer

Hepatic impairment

Thrombophilic disorders

Pregnancy