Gonadotropins: LH, FSH and related reproductive hormones

Main types and roles

The principal pituitary gonadotropins are Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH). In females, FSH promotes growth of ovarian follicles and LH triggers ovulation and supports the corpus luteum. In males, FSH supports sperm production while LH stimulates testosterone synthesis by Leydig cells. A related molecule, human chorionic gonadotropin (hCG), produced by the placenta, mimics LH activity during early pregnancy.

Structure and mechanism

Gonadotropins are glycoproteins composed of a common alpha subunit and a unique beta subunit that confers receptor specificity. They bind specific G protein–coupled receptors on gonadal cells, activating intracellular signaling that drives steroidogenesis and gametogenesis. Blood and urine assays measure their concentrations for diagnosis and monitoring.

Clinical importance and uses

Because of their central reproductive role, gonadotropins have many medical applications: recombinant FSH and LH are used in assisted reproduction to stimulate follicle development, and hCG is used to trigger ovulation or mimic LH. Conversely, hormonal contraceptives act by suppressing gonadotropin release. Abnormal levels can indicate pituitary disorders, gonadal failure, or pregnancy.

Notable facts and distinctions

• Gonadotropin release is pulsatile and regulated by GnRH feedback from sex steroids.
• hCG and LH share similar biological activity but differ in origin and clinical use.
• Monitoring gonadotropins guides fertility treatment and can help diagnose endocrine disorders.