From the Guidelines
A prolactin (PRL) test should be performed when a patient presents with symptoms suggesting hyperprolactinemia, such as delayed puberty, galactorrhoea, visual field loss, growth or pubertal arrest, or menstrual disturbance in girls. This is based on the strongest and most recent evidence from the consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence, which recommends offering serum prolactin measurement in children and young people (CYP) presenting with one or more of these signs and symptoms 1.
Key Indications for Prolactin Testing
- Delayed puberty
- Galactorrhoea
- Visual field loss
- Growth or pubertal arrest
- Menstrual disturbance in girls
Considerations for Testing
- A single prolactin measurement taken at any time of the day is sufficient to assess hyperprolactinaemia 1.
- Patients with elevated baseline prolactin (up to five times of the upper limit of normal) may require repeat sampling on a different day to differentiate stress-related hyperprolactinaemia from organic disease 1.
- The diagnosis of hyperprolactinaemia requires age-specific and sex-specific prolactin reference ranges and the exclusion of confounding conditions such as hypothyroidism, renal and/or hepatic impairment, and use of medications that cause hyperprolactinaemia 1.
Importance of Prolactin Testing
Prolactin testing is crucial for identifying abnormal levels, which can lead to appropriate treatment of underlying conditions affecting fertility and hormonal balance. It is also essential for evaluating pituitary masses, particularly when a prolactinoma is suspected, and for assessing patients with visual field defects or headaches that might indicate a pituitary tumor.
Additional Evaluations
In cases of mildly or incidentally elevated serum prolactin, assessing baseline macroprolactin levels is recommended to detect the possible presence of macroprolactin 1. Furthermore, excluding confounding diseases such as hypothyroidism, renal and/or hepatic impairment, and use of medications that cause hyperprolactinaemia is necessary for an accurate diagnosis 1.
Special Considerations
Medications can increase prolactin levels, including antipsychotics, some antidepressants, metoclopramide, and estrogens, so medication history should be reviewed 1. Stress can also elevate prolactin, and patients should rest for 30 minutes before blood collection. If elevated levels are found, repeat testing may be necessary to confirm the result, as transient elevations can occur.
From the Research
When to Do the Test for Prolactin
The test for prolactin (PRL) should be done in response to specific clinical presentations, including symptoms of hyperprolactinemia such as:
- Amenorrhea
- Galactorrhea It may also be performed as part of an infertility evaluation 2.
Conditions for Testing
An initial PRL level above the normal range should be followed by a repeat level from a blood sample drawn in the morning with the patient in a fasting state 2. The medical history and a few laboratory tests can eliminate the most common physiologic and pharmacologic causes of hyperprolactinemia, including:
- Pregnancy
- Primary hypothyroidism
- Treatment with drugs (such as neuroleptics) that reduce dopaminergic effects on the pituitary 2.
Special Considerations
In women with hyperprolactinemic amenorrhea, one important consequence of estrogen deficiency is osteoporosis, which deserves specific therapeutic consideration 3. Additionally, the occurrence of 'big big molecule of prolactin' (macroprolactinemia) may explain many cases of very high prolactin levels sometimes found in normally ovulating women and does not require any treatment 3, 4.
Treatment and Further Evaluation
Any confirmed hyperprolactinemia should be treated in a woman who wishes or fails to become pregnant, with preference given to cabergoline at the lowest possible dose that normalizes PRL 4. In cases where pituitary tumors are suspected, radiologic imaging of the sella turcica is necessary to establish whether a PRL-secreting pituitary adenoma or other lesion is present 2. Surgery is reserved for the patient with the uncommon tumor that does not respond to medical therapy or has a large cystic component or for the occasional patient who cannot tolerate dopamine agonists or who experiences pituitary apoplexy 2.