LH Function in Non-Pregnant Individuals
In the absence of hCG (i.e., in non-pregnant individuals), LH serves as the primary gonadotropin regulating gonadal steroidogenesis, gametogenesis, and ovulation in both sexes. 1, 2
Core Functions of LH
In Females
LH drives ovarian steroidogenesis by stimulating theca cells to produce androgens, which are then converted to estrogens by granulosa cells 1, 3
LH triggers ovulation through a mid-cycle surge that causes rupture of the mature follicle and release of the oocyte 1, 4
LH supports follicular maturation in the later stages of folliculogenesis, particularly after FSH priming has induced LH receptors on granulosa cells 4, 5
LH maintains the corpus luteum and stimulates progesterone secretion from small luteal cells, which is essential for preparing the endometrium for potential implantation 3, 2
LH acts preferentially through kinase pathways (pERK1/2 and pAKT) in ovarian cells, providing proliferative and antiapoptotic signals with partial agonism on progesterone production 2
In Males
LH stimulates testosterone production by binding to receptors on testicular Leydig cells 6, 1
LH regulates spermatogenesis indirectly through testosterone production, which provides essential support for sperm development 6, 7
LH maintains male sexual function by ensuring adequate testosterone levels for libido, erectile function, and secondary sexual characteristics 8
Key Physiologic Characteristics
Secretion Pattern
LH is secreted in a pulsatile manner from the anterior pituitary in response to pulsatile GnRH release from the hypothalamus 8, 1
LH has a relatively short half-life of approximately 90 minutes, requiring continuous pulsatile secretion to maintain gonadal function 2
Regulation
LH secretion is regulated by negative feedback from gonadal steroids (testosterone in males, estradiol and progesterone in females) acting on the hypothalamic-pituitary axis 6, 2
Reduced GnRH pulse frequency leads to decreased LH secretion and subsequent hypogonadism, as seen in functional hypothalamic amenorrhea 8
Clinical Implications
Timing in Assisted Reproduction
In natural cycles, IUI should be performed 1 day after LH rise to optimize timing with ovulation 8
LH testing is the most commonly applied method for timing intrauterine insemination in unstimulated cycles 8
Precocious Puberty
Premature pulsatile LH secretion (along with FSH) causes precocious puberty, defined as Tanner stage 2 breast development before age 8 years in girls 8
Elevated basal LH levels indicate premature activation of the hypothalamic-pituitary-gonadal axis 8
Hypogonadism
LH deficiency results in hypogonadotropic hypogonadism with impaired gonadal steroidogenesis and gametogenesis 8
Chronic suppression of LH pulse frequency from stress, excessive exercise, or energy deficit leads to functional hypothalamic amenorrhea 8
Important Distinction from hCG
While LH and hCG share the same receptor (LHCGR) and approximately 85% amino acid identity, they are not functionally equivalent 1, 2:
LH is produced by the pituitary in pulsatile fashion, while hCG is produced by trophoblast cells during pregnancy 1, 2
LH has a shorter half-life (~90 minutes) compared to hCG (hours), reflecting their different physiologic roles 2
LH and hCG activate different intracellular signaling pathways despite binding the same receptor, with LH preferentially activating kinase pathways and hCG showing stronger cAMP/PKA-mediated effects 2
hCG administration suppresses endogenous LH (and FSH) through negative feedback from increased testosterone production 6