lhormone

Lhormone, commonly abbreviated LH and formally known as luteinizing hormone, is a gonadotropin produced by the anterior pituitary gland. The term lhormone is sometimes used in texts as shorthand for LH. LH is essential for reproductive function in both sexes and works together with follicle-stimulating hormone (FSH) to regulate the gonads.

In females, LH participates in the ovarian cycle. It acts with FSH to promote follicle maturation, and a mid-cycle LH surge triggers ovulation, leading to the release of an oocyte. Following ovulation, LH supports the formation and function of the corpus luteum and stimulates ovarian production of progesterone, which helps prepare the endometrium for possible implantation.

In males, LH stimulates the Leydig cells of the testes to secrete testosterone, which is important for spermatogenesis and the development and maintenance of secondary sexual characteristics. Testosterone then exerts feedback control to modulate LH release.

Regulation of LH secretion is governed by gonadotropin-releasing hormone (GnRH) from the hypothalamus, released in pulsatile rhythms. Sex steroids such as estrogen, progesterone, and testosterone feed back to the pituitary and hypothalamus to influence GnRH and LH levels. LH secretion can also exhibit circadian variation.

Structure-wise, LH is a heterodimer composed of a common alpha subunit and a hormone-specific beta subunit. The LH receptor (LHR) on target cells is a G protein-coupled receptor; binding activates cAMP signaling and drives steroidogenesis in gonadal tissues.

Clinical relevance includes measurement of serum LH for diagnosing reproductive disorders and guiding fertility treatments. LH surges are detected with ovulation predictor kits, and in assisted reproduction, LH activity may be stimulated or mimicked using hCG or GnRH analogs to trigger ovulation. See also: luteinizing hormone, gonadotropins.