LUTEINIZING HORMONE (LH)
LH is a glycoprotein having weight about 30,000 kd .
FUNCTIONS:-
- In females, at the time of menstruation, FSH initiates follicular growth, specifically affecting granulosa cells. With the rise in oestrogens, LH receptors are also expressed on the maturing follicle that produces an increasing amount of estradiol. Eventually at the time of the maturation of the follicle, the oestrogen rise leads via the hypothalamic interface to the “positive feed-back” effect, a release of LH over a 24- to 48-hour period. This 'LH surge' triggersovulation, thereby not only releasing the egg but also initiating the conversion of the residual follicle into a corpus luteum that, in turn, producesprogesterone to prepare the endometrium for a possible implantation. LH is necessary to maintain luteal function for the first two weeks. In case of apregnancy, luteal function will be further maintained by the action of hCG (a hormone very similar to LH) from the newly established pregnancy. LH supports theca cells in the ovary that provide androgens and hormonal precursors for estradiol production.
- In the male, LH acts upon the Leydig cells of the testis and is responsible for the production of testosterone, an androgen that exerts both endocrine activity and intratesticular activity on spermatogenesis.
REGULATION:-
- It acts through cAMP messenger system.
- It is under the control of GnRH and has pulsatile secretion like GnRH.
- Also regulated by feedback effect of estrogen,progesterone and testosterone.
- Inhibin also prevents LH secretion. [13]
DISEASE STATE:-
High LH levels -Persistently high LH levels are indicative of situations where the normal restricting feedback from the gonad is absent, leading to a pituitary production of both LH and FSH. While this is typical in the menopause, it is abnormal in the reproductive years. There it may be a sign of:
- Premature menopause
- Gonadal dysgenesis, Turner syndrome
- Castration
- Swyer syndrome
- Polycystic Ovary Syndrome
- Certain forms of Congenital adrenal hyperplasia
- Testicular failure
Deficient LH activity- Diminished secretion of LH can result in failure of gonadal function (hypogonadism). This condition is typically manifest in males as failure in production of normal numbers of sperm. In females, amenorrhea is commonly observed. Conditions with very low LH secretions are:
- Kallmann syndrome
- Hypothalamic suppression
- Hypopituitarism
- Eating disorder
- Female athlete triad
- Hyperprolactinemia
- Gonadotropin deficiency
- Gonadal suppression therapy
- GnRH antagonist
- GnRH agonist (downregulation) [14]
LH blood test-
A normal result for am adult female is 5 to 25 IU/L. Levels peak around the middle of the menstrual cycle.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.[15]