What is prolactin?
Prolactin is a hormone secreted by the pituitary gland. It is involved in lactation and breast development.
What is a healthy prolactin level?
Different laboratories may use different reference ranges for prolactin, but the following ranges provide a rough guide:
- Healthy: <600mIU/l
- Modestly raised: 600–3000mIU/l
- Raised: 3000–6000mIU/l
- High: >6000mIU/l
Although <600mIU/l is classified as the “healthy” range, prolactin levels of 600–3000mIU/l in the "modestly raised” range can be healthy and don't necessarily indicate an underlying disease. Prolactin levels can be influenced by a variety of factors, such as stress and exercise.
What causes prolactin levels to rise?
Prolactin levels of 600–3000mIU/l can be caused by a range of factors, including stress, exercise, nipple stimulation, chest binding, and pregnancy.
Some drugs also cause prolactin levels to rise. These include antipsychotics (especially risperidone), antidepressants, and anti-nausea medication (such as domperidone and metoclopramide).
Some medical conditions can raise prolactin levels to “modestly raised”. These include polycystic ovarian syndrome, hypothyroidism, and kidney disease.
Prolactin levels within the “raised” and “high” levels may be caused by a prolactinoma. This is very rare. This is a usually benign tumour of the pituitary gland that secretes prolactin. However, a prolactinoma is usually associated with prolactin levels above 3000mIU/l. If your prolactin level is below 3000mIU/l, then you are very unlikely to have a prolactinoma.
What are the symptoms of a prolactinoma?
Prolactinoma symptoms include visual disturbances, headaches, dizziness, loss of balance, nausea, and vomiting. These occur when the tumour reaches a significant size.
Also, as noted above, a prolactinoma is usually associated with prolactin levels above 3000mIU/l. If your prolactin level is below 3000mIU/l and you have none of the symptoms, then it is very unlikely that you have a prolactinoma.
Can gender affirming hormone treatment cause prolactinoma?
No. There is no evidence that gender affirming hormone treatment causes prolactinoma. People who are receiving gender affirming hormone treatment are no more likely to develop a prolactinoma than people who are not receiving gender affirming hormone treatment.
How will gender affirming hormone treatment affect my prolactin levels?
Feminising hormone treatment with oestrogen can raise prolactin levels. Cyproterone acetate can also sometimes slightly raise prolactin levels. The raised prolactin levels due to feminising hormone treatment usually remain within the “modestly raised” range and do not cause any clinically significant problems. There is no need for routine checking of prolactin levels.
There is no need for people receiving gender affirming hormone treatment to screen for prolactinoma, unless there are neurological symptoms.
When should I check my prolactin level?
If you have neurological symptoms, such as visual disturbances, headaches, dizziness, loss of balance, nausea, and vomiting, then you are strongly recommended to seek medical attention from your doctor. Your doctor will perform an examination and may include a prolactin level as part of the investigations to arrive at a diagnosis.
What do I do if I have had a blood test for prolactin and it shows that my prolactin level is raised?
If your prolactin level is above 3000mIU/l or you have prolactinoma symptoms, we recommend that you seek medical attention urgently. Your doctor can then arrange tests to investigate for a prolactinoma.
If your prolactin level is 1000–3000mIU/l, then it is unlikely that you have a prolactinoma. We recommend that you see your doctor on a routine basis to investigate other potential causes of the raised prolactin. This might include checking your thyroid and reviewing your medication history. There may be no underlying medical cause, because prolactin can be raised by stress, exercise, and nipple stimulation.
If your prolactin level is <1000mIU/l and you have no symptoms, then no further action or monitoring is required.
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