Luteinizing Hormone (LH) ELISA
The DRG LH ELISA Kit is an enzyme immunoassay for the quantitative in vitro diagnostic measurement of the Luteinizing Hormone (LH) in serum.
Luteinizing hormone (LH) is produced in both men and women from the anterior pituitary gland in response to luteinizing hormone-releasing hormone (LH-RH or Gn-RH), which is released by the hypothalamus (1-3). LH, also called interstitial cell-stimulating hormone (ICSH) in men, is a glycoprotein with a molecular weight of approximately 30.000 daltons (4). It is composed of two non covalently associated dissimilar amino acid chains, alpha and beta (5). The alpha chain is similar to that found in human thyroid-stimulating hormone (TSH), follicle stimulating hormone (FSH), and human chorionic gonadotropin (hCG). The difference between these hormones lie in the amino acid composition of their beta subunits, which account for their immunological differentiation (6-8). The basal secretion of LH in men is episodic and has the primary function of stimulating the interstitial cells (Leydig cells) to produce testosterone. The variation in LH concentrations in women is subject to the complex ovulatory cycle of healthy menstruating women, and depends upon a sequence of hormonal events along the gonado-hypothalamic-pituitary axis. The decrease in progesterone and estradiol levels from the preceeding ovulation initiates each menstrual cycle (9,10). As a result of the decrease in hormone levels, the hypothalamus increases the secretion of gonadotropin-releasing factors (GnRF), which in turn stimulates the pituitary to increase FSH production and secretion (4).
The rising FSH levels stimulate several follicles during the follicular phase, one of these will mature to contain the egg. As the follicle develops, estradiol is secreted, slowly at first, but by day 12 or 13 of a normal cycle increasing rapidly. LH is released as a result of this rapid estradiol rise because of direct stimulation of the pituitary and increasing GnRF and FSH levels. These events constitute the pre-ovulatory phase (11).
Ovulation occurs approximately 12 to 18 hours after the LH reaches a maximum level. After the egg is released, corpus luteum is formed which secretes progesterone and estrogen – two feedback regulators of LH (3,10). The luteal phase rapidly follows this ovulatory phase, and is characterized by high progesterone levels, a second estradiol increase, and low LH and FSH levels (12).
Low LH and FSH levels are the result of the negative feedback effects of estradiol and progesterone on the hypotalamic-pituitary axis. After conception, the developing embryo produces hCG, which causes the corpus luteum to continue producing progesterone and estradiol. The corpus luteum regresses if pregnancy does not occur, and the corresponding drop in progesterone and estradiol levels results in menstruation. The hypothalamus initiates the menstrual cycle again as a result of these low hormone levels (12).
The DRG LH ELISA Kit is a solid phase enzyme-linked immunosorbent assay (ELISA) based on the sandwich principle. The microtiter wells are coated with a monoclonal [mouse] antibody directed towards a unique antigenic site on a LH molecule. An aliquot of patient sample containing endogenous LH is incubated in the coated well with enzyme conjugate, which is an anti-LH monoclonal antibody conjugated with horseradish peroxidase. After incubation the unbound conjugate is washed off. The amount of bound peroxidase is proportional to the concentration of LH in the sample. Having added the substrate solution, the intensity of colour developed is proportional to the concentration of LH in the patient sample.
- Harris, G.W. and Naftolinf., The Hypothalamus and Control of Ovulation, Brit. Med. Bullet., 26, 1-9 (1970).
- Knobil, E., The Neuroendocrine Control of the Menstrual Cycle, Rec. Prog. Horm Res., 36, 52-88 (1980).
- Jeffcoate, S.L., Clinics in Endocrinol. Metab., 4, 521-543 (1975).
- Whitely, R.J., Keutmann, H.T. and Ryan, R.J., Endocrinology, 102, 1874 (1978).
- Pierce, J.G. and Parsons, T.F., Glycoprotein hormones: Structure and Function, Annual Rev. Biochem., 50, 465-495 (1981).
- Bardin , C.W. and Paulsen, C.A., “The Testes” in Textbook of Endocrinology, (ed.) R.H. Williams M.D., W.B. Saunders Co., (1981).
- Shome, B. and Parlow, A.F., J. Clin. Endocrinol. Metabl., 39, 199-202 (1974).
- Shome, B. and Parlow, A.F., J. Clin. Endocrinol. Metabl., 39, 203-205 (1974).
- Ross, G.T., VandeWeile, R.L., and Frantz, A.G. Chapter 7 in “The Ovaries and the Breasts” in “Textbook of Endocrinology” (R. H. Williams, Ed.), W.B. Saunders Co. (1981).
- Marshall, J.C., Clinics in Endocrinal Metab., 4, 545-567 (1975).