Prolactin is a hormone secreted by the pituitary gland to promote milk production, lactation.
As one might expect, levels of this hormone are markedly elevated during periods of lactation. Normal lactation generally occurs following a recent birth, prolactin can be considered to be “nature’s contraceptive”. In primitive societies this offers the new mother protection from another pregnancy too soon. High levels of prolactin inhibit ovulation and normally there are no periods during lactation. In the patient who is trying to conceive and menstrual cycles are not regular, excess prolactin is among the possible causes.
It has become part of the screening for most infertility patients. Some women who have high prolactin will produce small amounts of milk, perhaps noted only by expression of the nipple. It is important to investigate the cause since elevated prolactin levels may occur as a consequence of a prolactin producing pituitary tumor or other tumors in the brain. In addition, the use of certain drugs: (tranquilizers, ganglion blocker antihypertensives, antidepressants, thiazides and narcotics) can elevate the blood prolactin level. Nipple stimulation can cause mild elevations as can food and stress. Therefore, it is usual practice to test serum prolactin levels by drawing the blood sample in the morning, before eating breakfast. Borderline elevations should be rechecked and if persistently elevated, additional tests such as brain scans by MRI may be needed.
Another important consideration is that mild to moderately raised prolactin levels often present as one of the earliest signs of an impending or existing hypothyroid state. In women, hypothyroidism is most often due to an autoimmune process (Hashimoto’s Disease) which slowly destroys thyroid hormone producing tissue until the point is reached where clinical/biochemical and physical manifestations of hypothyroidism appear. Absent, irregular or heavy menstrual periods may occur. Most of the time there are no specific symptoms, but these may include some or all of the following: raised blood, an enlarged thyroid gland weight gain, weakness, intolerance of cold weather, lethargy, depression, dryness of the skin, hair loss, visual disturbances, recurrent pregnancy loss and/or infertility.
In these cases, TSH will be elevated and the normal thyroid function tests will be low or normal. Autoimmune blood changes are almost always present in the form of antithyroid antibodies (ATA) such as antithyroglobulin and/or antimicrosomal antibodies, the presence of which may antedate the appearance of clinical hypothyroidism by many years (often by decades). Accordingly, an elevated prolactin blood level, regardless of severity, demands investigation.
Pituitary adenomas that cause a profound increase in blood prolactin levels are usually treated effectively with prolonged Parlodel therapy, even during pregnancy. Larger tumors might require surgery but fortunately this is the exception rather than the rule. Drug-induced hyperprolactinemia can sometimes be ameliorated by adjusting or by withdrawing the causative agent. In situations of hypothyroidism, hyperprolactinemia usually responds well to appropriate thyroid hormone replacement therapy.
This information is provided by New York Fertility Services for patient information. Diagnostic and treatment services, including low cost IVF for couples trying to get pregnant, are provided in New York City at 16 E. 40th Street.