Hyperprolactinemia

Hyperprolactinaemia (BE) or hyperprolactinemia (AmE) is the term given to having too high levels of prolactin in the blood. (Normal levels are less than 580 mIU/L for women, and less than 450 mIU/L for men.) more...

The hormone prolactin is downregulated by dopamine and is upregulated by estrogen. A falsely high measurement may occur due to the presence of the biologically inactive macroprolactin in the serum. This can show up as high prolactin in some types of tests, but is asymptomatic.

Causes

Hyperprolactinaemia may be caused by either disinhibition (eg compression of the pituitary stalk or reduced dopamine levels) or excess production from a prolactinoma (a pituitary gland adenoma tumour). A prolactin level of 1000-5000mIU/L could be from either mechanism, but >5000mIU/L is likely due to an adenoma with macro-adenomas (large tumours over 10mm diameter) having levels of up to 100,000mIU/L.

Physiological causes

(i.e. as result of normal body functioning): Pregnancy, breastfeeding, stress, sleep.

Prescription Drugs

(the most common cause of hyperprolactinaemia). Prolactin secretion in the pituitary is normally suppressed by the brain chemical, dopamine. Drugs that block the effects of dopamine at the pituitary or deplete dopamine stores in the brain may cause the pituitary to secrete prolactin. These drugs include the major tranquilizers (phenothiazines) trifluoperazine (Stelazine) and haloperidol (Haldol); metoclopramide (Reglan), used to treat gastroesophageal reflux and the nausea caused by certain cancer drugs; and less often, alpha-methyldopa and reserpine, used to control hypertension. Finally oestrogens and TRH.

Diseases

Prolactinoma or other tumors arising in or near the pituitary--such as those that cause acromegaly or Cushing's syndrome--may block the flow of dopamine from the brain to the prolactin-secreting cells, likewise division of the pituitary stalk or hypothalamic disease. Other causes include chronic renal failure, hypothyroidism and sarcoidosis. Some women with polycystic ovary syndrome may have mildly elevated prolactin levels.

Apart from diagnosing hyperprolactinaemia and hypopituitarism, prolactin levels are often determined by physicians in patients who have suffered a seizure, when there is doubt whether this was an epileptic seizure or a non-epileptic seizure. Shortly after epileptic seizures, prolactin levels often rise, while they are normal in non-epileptic seizures.

Idiopathic

In many patients elevated levels remain unexplained and may represent a form of hypothalamic-pituitary dysregulation.

Symptoms

In women, a high blood level of prolactin often causes hypoestrogenism with anovulatory infertility and a decrease in menstruation. In some women, periods may disappear altogether (amenorrhea). In others, periods may become irregular or menstrual flow may change. Women who are not pregnant or nursing may begin producing breast milk. Some women may experience a loss of libido (interest in sex). Intercourse may become painful because of vaginal dryness.

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