Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) are both helpful in the determination of menopause. Furthermore, they are integral in the evaluation of suspected gonadal failure. Infertility evaluations also include these tests.
LH and Follicle-Stimulating Hormone are glycoproteins produced in the anterior pituitary gland in response to stimulation by gonadotropin-releasing hormone (GNRH), previously called luteinizing-releasing hormone. GNRH is stimulated when circulating levels of estrogen (in females) or testosterone (in males) are low. Through a feedback mechanism, GNRH is stimulated by the hypothalamus, which in turn stimulates the production and release of Luteinizing Hormone and Follicle-Stimulating Hormone. These two hormones then act on the ovary or testes. In the female, Follicle-Stimulating Hormone stimulates the development of follicles in the ovary. In the male, Follicle-Stimulating Hormone stimulates Sertoli cell development.
In the female, Luteinizing Hormone stimulates follicular production of estrogen, ovulation, and formation of a corpus luteum. In the male, Luteinizing Hormone stimulates testosterone production from the Leydig cells. In the end, estrogen or testosterone is produced, which in turn inhibits Follicle-Stimulating Hormone and Luteinizing Hormone. Follicle-Stimulating Hormone is necessary for maturation of the ovaries and testes. Follicle-Stimulating Hormone and Luteinizing Hormone are necessary for sperm production. In the female these hormones are secreted differently at different times in the menstrual cycle. The midcycle peak of Follicle-Stimulating Hormone is necessary for follicle/ovum formation. Luteinizing Hormone also must peak about that same time to stimulate ovulation or corpus luteal formation that could potentially support an embryo if fertilization were to occur.
Earlier bioassays could not distinguish Follicle-Stimulating Hormone from Luteinizing Hormone. Therefore they were often measured together. For that matter, early bioassays often included thyroid-stimulating hormone and human chorionic gonadotropin. Now, with the use of monoclonal antibodies and better immunoassays, these hormones can each be measured separately and accurately.
LH is secreted in a pulsatile manner. One specimen may not accurately indicate total body levels of this hormone. Often several specimens of blood are obtained 20 to 30 minutes apart, and the blood is pooled or results of each are averaged. The variable nature of Luteinizing Hormone can be diminished by measuring Luteinizing Hormone in a 24-hour urine sample. The disadvantage is that Luteinizing Hormone values can be falsely low because of dilution with large urine volumes. Spot urine tests have become very useful in the evaluation and treatment of infertility. Because Luteinizing Hormone is rapidly excreted into the urine, the plasma Luteinizing Hormone surge that precedes ovulation by 24 hours can be recognized quickly and easily. This is used to indicate the period when the woman is most fertile. The best time to obtain a urine specimen is between 11 AM and 3 PM. Usually the woman begins to test her urine on the 10th day following the onset of her menses and continues to do so daily. Home kits using a color change as an end point are now marketed to make this process even more convenient.
These hormones are used in the evaluation of infertility. Performing an Luteinizing Hormone assay is an easy way to determine if ovulation has occurred. An Luteinizing Hormone surge in blood levels indicates that ovulation has taken place. Under the influence of LH, the corpus luteum develops from the ruptured Graafian follicle. Daily samples of serum Luteinizing Hormone around the middle of the woman’s cycle can detect the Luteinizing Hormone surge, which is thought to occur on the day of maximal fertility.
These assays also determine whether a gonadal insufficiency is primary (problem with the ovary/testicle) or secondary (caused by pituitary insufficiency resulting in reduced levels of Follicle-Stimulating Hormone and Luteinizing Hormone). Elevated levels of Follicle-Stimulating Hormone and Luteinizing Hormone in patients with gonadal insufficiency indicate primary gonadal failure, as may be seen in women with polycystic ovaries or during menopause. In secondary gonadal failure, Luteinizing Hormone and Follicle-Stimulating Hormone levels are low as a result of pituitary failure or some other pituitary-hypothalamic impairment, stress, malnutrition, or physiologic delay in growth and sexual development.
FSH and Luteinizing Hormone assays are often done to diagnose menopause. Luteinizing Hormone hormones are also used to study testicular dysfunction in men and to evaluate endocrine problems related to precocious puberty in children. The use of these hormone assays can also help in the evaluation of disorders of sexual differentiation, such as Klinefelter syndrome.
Normal Luteinizing Hormone Levels
Male Children under 10 years of age: Between 0.04 and 3.6 international units/L.
Female Children under 10 years of age: Between 0.03 and 3.9 international units/L.
Adult males: Between 1.24 and 7.8 international units/L.
Normal Luteinizing Hormone Levels for Adult Females
Follicular Phase: Between 1.68 and 15 international units/L.
Ovulatory Peak: Between 21.9 and 56.6 international units/L.
Luteal Phase: Between 0.61 and 16.3 international units/L.
Postmenopause: Between 14.2 and 52.3 international units/L.
Normal Follicle-Stimulating Hormone Levels
Male Children under 10 years of age: Between 0.3 and 4.6 international units/L.
Female Children under 10 years of age: Between 0.68 and 6.7 international units/L.
Adult males: Between 1.42 and 15.4 international units/L.
Normal Follicle-Stimulating Hormone Levels for Adult Females
Follicular Phase: Between 1.37 and 9.9 international units/L.
Ovulatory Peak: Between 6.17 and 17.2 international units/L.
Luteal Phase: Between 1.09 and 9.2 international units/L.
Postmenopause: Between 19.3 and 100.6 international units/L.
Causes of Luteinizing Hormone and Follicle-Stimulating Hormone False Indications
- Recent use of radioisotopes may affect test results if the testing method is performed by radioimmunoassay. The previously administered radioisotope may interfere with the results.
- Human chorionic gonadotropin (hCG) and thyroid-stimulating hormone (TSH) may interfere with some immunoassay methods because of the similarities of part of the hormone molecule. Therefore patients with hCG-producing tumors and those with hypothyroid should be expected to have falsely high Luteinizing Hormone levels.
- Drugs that may increase Luteinizing Hormone or Follicle-Stimulating Hormone levels include anticonvulsants, cimetidine, clomiphene, digitalis, levodopa, naloxone, and spironolactone.
- Drugs that may decrease Luteinizing Hormone levels include digoxin, estrogens, oral contraceptives, progesterones, steroids, testosterone, and phenothiazines.
Causes of High Luteinizing Hormone and Follicle-Stimulating Hormone Levels.
- Gonadal Failure including Physiologic Menopause, Ovarian Dysgenesis (Turner Syndrome), Testicular Dysgenesis (Klinefelter Syndrome), Castration, Anorchia, Hypogonadism, Polycystic Ovaries, Complete Testicular Feminization Syndrome: Decreased levels of estrogen or testosterone occur with gonadal failure. Through a feedback mechanism, Follicle-Stimulating Hormone and Luteinizing Hormone secretion is stimulated maximally.
- Precocious Puberty: One cause of precocious puberty is oversecretion of Follicle-Stimulating Hormone and LH.
- Pituitary Adenoma: Some pituitary adenomas secrete Follicle-Stimulating Hormone or Luteinizing Hormone without regard to any feedback mechanism.
Causes of Low Luteinizing Hormone and Follicle-Stimulating Hormone Levels.
- Pituitary Failure: Follicle-Stimulating Hormone and Luteinizing Hormone are produced in the anterior pituitary. The first indication of pituitary failure is reduction of FSH/LH and the resulting gonadal failure.
- Hypothalamic Failure: GNRH is produced in the hypothalamus and stimulates FSH/LH production. Failure of that portion of the brain to produce GNRH will cause reduced FSH/LH levels.
The following conditions are assoctiated with Low Luteinizing Hormone and Follicle-Stimulating Hormone Levels. However, the pathophysiology of these observations is not clear:
- Anorexia Nervosa.