Prolactin Test Dubai — Hormone Level Screening

Prolactin is a 199 amino acid polypeptide hormone produced by lactotroph cells in the anterior pituitary gland. Its primary role is initiating and maintaining lactation after childbirth, stimulated by oestrogen during pregnancy and nipple stimulation. Outside of pregnancy and breastfeeding, prolactin has significant roles in regulating the reproductive axis by suppressing GnRH pulsatility. The prolactin blood test measures the serum concentration in mIU/L or ng/mL, with normal ranges typically below 500 mIU/L (23 ng/mL) in women and below 450 mIU/L (21 ng/mL) in men outside of pregnancy and breastfeeding. Levels vary between laboratories, so local reference ranges apply.

Causes span physiological, pharmacological, and pathological categories. Physiological elevation occurs with pregnancy, breastfeeding, sleep (prolactin peaks during sleep), stress, exercise, sexual intercourse, and nipple stimulation. Pharmacological causes include antipsychotic medications (dopamine antagonists such as haloperidol, risperidone, metoclopramide, and domperidone are particularly potent prolactin-elevating drugs), antidepressants, opioids, and antihypertensives including verapamil. Pathological causes include prolactinoma (the most common pituitary tumour), other pituitary or hypothalamic masses causing pituitary stalk compression (stalk effect), hypothyroidism (TRH stimulates prolactin), chronic kidney disease, and liver cirrhosis.

The degree of prolactin elevation provides diagnostic guidance. Levels mildly elevated above the upper reference limit, typically below 2,000 to 3,000 mIU/L, may represent physiological variation, medication effects, or macroprolactinaemia (a benign form discussed below). Moderate elevation from 2,000 to 5,000 mIU/L may be seen with microprolactinoma or stalk compression from a non-functioning tumour. Levels consistently above 5,000 mIU/L, and especially above 10,000 mIU/L, are strongly associated with macroprolactinoma. Very high levels exceeding 100,000 mIU/L are diagnostic of macroprolactinoma. MRI of the pituitary with gadolinium contrast is the imaging investigation of choice when a prolactinoma is suspected.

Macroprolactin is prolactin bound to IgG antibodies, forming a large complex that is biologically inactive but detected by standard prolactin immunoassays, causing apparent hyperprolactinemia on blood testing. Macroprolactinaemia is found in 10 to 26 percent of patients with elevated prolactin on standard assay and is usually clinically benign — these patients have no symptoms of true hyperprolactinemia and require no treatment. The distinction is made by polyethylene glycol (PEG) precipitation, which removes the bound complexes, leaving only free biologically active prolactin. A post-PEG recovery below 40 percent confirms macroprolactinaemia. Without this test, macroprolactinaemia may be incorrectly diagnosed as pathological, leading to unnecessary MRI scans and treatments. Our laboratory offers macroprolactin exclusion testing.

Yes. Hypothyroidism is an important and frequently overlooked cause of secondary hyperprolactinemia. Reduced thyroid hormone levels stimulate increased thyrotropin-releasing hormone (TRH) from the hypothalamus, which stimulates not only TSH but also prolactin release from the pituitary. Additionally, prolonged hypothyroidism can cause the pituitary to enlarge with thyrotroph hyperplasia, which may be mistaken for a pituitary adenoma on imaging. Crucially, treating the underlying hypothyroidism with levothyroxine normalises TSH levels, reduces TRH drive, and resolves both the hyperprolactinemia and any pituitary enlargement — without specific prolactin-lowering treatment. This is why TSH should always be measured alongside prolactin.

Treatment depends on the cause and severity. For prolactinoma, dopamine agonists (cabergoline first-line, bromocriptine second-line) are highly effective, normalising prolactin in over 85 percent of cases and shrinking tumour size in the majority of macroprolactinomas, often obviating the need for surgery. Cabergoline is taken twice weekly and is well tolerated. Treatment is typically continued for at least 2 years, after which a trial of withdrawal can be considered if prolactin has normalised and MRI shows no residual tumour. Surgery (transsphenoidal adenomectomy) is reserved for dopamine agonist-resistant or intolerant cases and for decompression of vision-threatening tumours. For medication-induced hyperprolactinemia, switching or reducing the offending drug resolves the elevation.

In men, elevated prolactin suppresses GnRH pulsatility, reducing LH and FSH, which in turn decreases testicular testosterone production and impairs spermatogenesis. The clinical consequences include reduced libido, erectile dysfunction, decreased ejaculate volume, oligozoospermia or azoospermia, and gynaecomastia (breast tissue development from the altered androgen-estrogen ratio). These effects are often gradual and may be attributed to other causes before prolactin is checked. Male hyperprolactinemia is less common than in women and is more frequently caused by macroprolactinoma due to the longer delay before symptoms prompt investigation. Dopamine agonist treatment restores testosterone, improves libido and sexual function, and can restore fertility.

Yes, significantly. Prolactin is a stress-responsive hormone released in response to physical and psychological stress, including the anxiety of venepuncture itself. Exercise raises prolactin acutely for up to 30 to 60 minutes after vigorous activity. Nipple stimulation and sexual activity cause transient prolactin spikes. Sleep is associated with a pronounced nocturnal prolactin surge. To minimise these confounders, morning testing is preferred, ideally with a period of rest in the waiting room before sample collection. Significantly elevated prolactin should be confirmed with at least one repeat measurement under standardised conditions, and macroprolactin exclusion performed before initiating further investigation or treatment.