Prolactin is a protein hormone that in female mammals initiates and maintains the secretion of milk, the mammary glands having been previously prepared for this function by the action of other hormones. In the female rat, prolactin also maintains the secretion of the hormone progesterone , which is formed by the corpus luteum , an endocrine gland of the ovary . Thus, prolactin is a gonadotropin , its target being an endocrine gland. Moreover, the molecular structures of prolactin and growth hormone are similar, which may explain why they show some overlap in biological properties. In particular, administration of prolactin promotes some growth in many terrestrial vertebrates. Human growth hormone has prolactin-like luteotropic properties.
Using appropriate tests for monitoring hormone therapy is crucial in establishing the appropriate dosing regimen. This reduces the chance of undesirable side effects and maximizes beneficial effects. For example, excessive use of androgens (testosterone, androstenedione, DHEA, and testosterone derivatives) can activate subclinical prostate tumors which are androgen-dependent. Monitoring is especially important in older males. By the age of 70, at least 50% of men have subclinical prostate cancer. These men are especially susceptible to prostate growth stimulation by androgens.
Other side effects include increased risk of heart problems in older men with poor mobility, according to a 2009 study at Boston Medical Center. A 2017 study published in JAMA found that treatments increase coronary artery plaque volume. Additionally, the Food and Drug Administration (FDA) requires manufactures to include a notice on the labeling that states taking testosterone treatments can lead to possible increased risk of heart attacks and strokes. The FDA recommends that patients using testosterone should seek medical attention right away if they have these symptoms: