Routine Diagnosis of Hyperprolactinemia

What are the conventional methods for diagnosing hyperprolactinemia? Hyperprolactinemia is the most common pituitary disease, with galactorrhea and hypogonadism as prominent manifestations. Female patients may have decreased libido and loss of sexual desire, which will be relieved after treatment as PRL levels decrease.

Patients with galactorrhea and hypogonadism should consider the possibility of high PRL, which can be diagnosed by measuring blood PRL. Normal male blood PRL generally does not exceed 0.68nmol/L (15ng/ml), and female blood PRL is generally 0.23-0.91nmol/L (5-20ng/ml). Since PRL is pulsatile and affected by many factors, it is best to repeat the measurement. It is worth noting that a few people have normal blood PRL in the morning but elevated blood PRL at night. These patients need to measure the nighttime blood PRL level and do a provocation test. Commonly used provocation tests include TRH test and metoclopramide (metoclopramide) test. The TRH excitation test is to inject TRH 400-500ug intravenously on an empty stomach, and collect blood for PRL at 0, 15, 30, 45, 60, 90, and 120 minutes respectively. After normal people are injected with TRH, PRL increases, and the peak value appears 15-30 minutes after injection, which is about 5 times the base value (3-5 times for men and 5-8 times for women). The dose of metoclopramide test is 10 mg, which can be taken orally, or injected intravenously or intramuscularly. The PRL peak value appears 60 to 120 minutes after oral administration, and the peak value appears 20 to 60 minutes after intravenous or intramuscular injection. The peak value of normal people is more than 3 times the base value. PRL tumor patients are slow to respond to TRH and metoclopramide, and the multiple increase of PRL after administration is not as high as that of normal people, but the absolute value of the increase is higher than that of normal people.

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1. Laboratory examination

Prolactin measurement: Take blood samples on an empty stomach 1 to 2 hours after getting up in the morning to measure PRL. The normal value of PRL on an empty stomach is 0.23 to 1.14 nmol/L (5 to 25 ng/ml). Women have higher levels than men. PRL has a peak secretion related to sleep, usually 1 to 2 hours after falling asleep. Pregnant women's PRL can increase 10 times, and the baby's sucking can cause an acute increase in PRL, which returns to normal after 2 to 3 hours. 4 to 6 weeks after delivery, PRL returns to pre-pregnancy levels. Prolactin>9.1nmol/L (200ng/L) is seen in prolactinoma and chronic renal failure. Other causes of hyperprolactinemia include postpartum lactation, functional hyperprolactinemia, hypothalamic lesions such as sarcoma, histiocytosis, parasellar tumors, pituitary stalk lesions and some drugs that reduce dopamine production, including methyldopa, reserpine, tricyclic antidepressants, phenothiazines, etc. Metoclopramide increases prolactin to 4.5-6.8nmol/L (100-150ng/ml). Prolactin levels may also increase in people with primary hypothyroidism, chest wall diseases and spinal cord lesions.

2. Other auxiliary examinations

(1) Due to TSH and GH deficiency in children, bone X-rays may show decreased bone age.

(2) CT and MRI examinations are of great significance for diagnosis. These two examinations can show the location, size, presence of cystic changes, invasion of the tumor into adjacent brain tissue, and whether hydrocephalus exists.