Luteinizing Hormone

Luteinizing Hormone a.k.a. Lutropin. It is a hormone that is produced by the anterior pituitary gland. They are under complex regulation by hypothalamic gonadotropin-releasing hormone and by gonadal sex hormones (estrogen and progesterone in females and testosterone in males). Luteinizing hormone acts on Leydig's (interstitial) cells of the gonads. For females, an acute rise of LH will trigger the ovulation, while for males, where LH had also been called Interstitial Cell Stimulating Hormone (ICSH), wherein it stimulates Leydig cell the production of testosterone which stimulates and maintains spermatogenesis. This steroid hormone is synthesized from cholesterol in the testes and is the principal androgen. It is lipid soluble and readily diffuses out of Leydig cell into the interstitial fluid and then into the blood. Testosterone acts in a negative feedback manner to suppress secretion of LH by anterior pituitary gonadotrophs and to suppress secretion of GnRH by hypothalamic neurosecretory cells. In some target cells, such as those in the prostate and seminal vesicles, the enzyme 5 alpha-reductase converts testosterone to another androgen called dihydrotestosterone (DHT).

Photo source: http://graphics8.nytimes.com/images/2007/08/01/health/adam/17228.jpg

Purpose for testing

○ To detect ovulation
○ To assess male or female infertility
○ To evaluate amenorrhea
○ To monitor therapy designed to induced ovulation

Reference values for LH:
♀Female

Follicular ------------------------- 1.37 to 9.9 mIU/L
Ovulatory peak ------------------ 6.17 to 17.2 mIU/L
Luteal ---------------------------- 1.09 to 9.2 mIU/L
Postmenopausal ----------------- 19.3 to 100.6 mIU/L
♂Male -------------------------- 1.42 to 15.4 mIU/L

Procedure and posttest care

♦ Perform a venipuncture, and collect the sample in a 7-ml clot-activator tube.
♦ Apply direct pressure to the venipuncture site until bleeding stops.
♦ If a hematoma develops at the venipuncture site, apply warm soaks.
♦ Instruct the patient that he/she may resume medications discontinued before tests as ordered.

Precautions

• Handle the sample gently to prevent hemolysis.
• If the patient is a female, indicate the phase of her menstrual cycle on the laboratory request. Make a note if the patient is menopausal.

Abnormal Findings

♀In women, absence of a mid-cycle peak in plasma LH levels may indicate anovulation. Decreased or low-normal plasma may indicate hypogonadism; these findings are commonly associated with amenorrhea. High plasma LH levels may indicate congenital absence of ovaries or ovarian failure associated with Stein-Leventhal syndrome (polycystic ovary syndrome), Turner's syndrome (ovarian dysgenesis), menopause or early stage acromegaly. Infertility can result from primary or secondary gonadal dysfunction.
♂In men, low plasma LH values may indicate secondary gonadal dysfunction (of hypothalamic or pituitary origin); high values may indicate testicular failure (primary hypogonadism) or destruction or congenital abscence of testes.


Interfering factors
◘ Recently administered radioisotopes.
◘ Hemolysis of blood sample.
◘ Estrogen or oral contraceptives, testosterone.
◘ Several drugs affect test outcome.
◘ Pregnancy.





References:

☺A Manual of Laboratory and Diagnostic Tests 7th Edition
by Frances Fischbach

☺Professional Guide to Diagnostic Tests

☺Clinical Chemistry Principles, Procedures, Correlations 5th Edition
by Michael L. Bishop, Edward P. Fody, Larry E. Schoeff

☺Principles of Anatomy and Physiology 10th Edition
by Gerard Tortora, Sandra Reynolds Grabowski

☺http://en.wikipedia.org