Hormones · Blood

Prolactin

Pituitary hormone for milk production; raised by stress, medicines or a benign pituitary tumor.

At a glance

Measured in blood
In 6 test panels
Check the preparation

Explanation

Prolactin: what is measured?

Prolactin is made in the pituitary gland and drives milk production after childbirth. Outside pregnancy and breastfeeding the value is low, because the brain substance dopamine inhibits its release. Too high a prolactin suppresses the signals to the ovaries and testes, resulting in absent periods, less interest in sex or erection problems. The value rises temporarily with stress, pain, sleep, after a meal and after breast stimulation.

What can it detect?

Hyperprolactinemia (too much prolactin) as the cause of absent or irregular periods, infertility, milk discharge, less interest in sex or erection problems
Prolactinoma: a benign tumor of the pituitary gland that makes prolactin
Side effect of medicines that block dopamine (antipsychotics, some antidepressants and medicines for nausea)
Reduced function of the pituitary gland (low prolactin, rare)

Result

What does the result mean?

Prolactin too high

A slightly raised prolactin is often due to stress around the blood draw, lack of sleep, a meal, breast stimulation or intensive exercise, and is usually normal when repeated. Other common causes are medicines that block dopamine (antipsychotics, metoclopramide, domperidone, some antidepressants), estrogens, an underactive thyroid, reduced kidney function, pregnancy and breastfeeding. With a very high value, a prolactinoma is likely: a benign tumor of the pituitary gland that is usually small in women and more often large in men, sometimes with headache or loss of part of the visual field. Symptoms that go with a raised prolactin: absent or irregular periods, milk discharge, less interest in sex, erection problems, infertility and, in the long term, bone loss. Some of the 'raised' results are due to macroprolactin, a harmless bound form that the laboratory can check separately.

Prolactin too low

A low prolactin usually has no meaning and causes no symptoms. It fits the use of dopamine-like medicines (including cabergoline, bromocriptine and levodopa) or, rarely, reduced function of the pituitary gland as a whole. After childbirth, a low prolactin can go together with a lack of milk production.

After an abnormal result

The GP repeats a raised value at rest and fasting, looks at medicines, pregnancy, thyroid and kidney function, and has macroprolactin checked if needed. With a repeatedly clearly raised value, referral to an internist-endocrinologist follows, usually with an MRI of the pituitary gland.

Reliability

How reliable is the test?

A single slightly raised value proves nothing, because prolactin reacts strongly to stress, food and medicines; a repeat test at rest, fasting and at least an hour after getting up is the first step. The level of the value does say something: the higher it is, the greater the chance of a prolactinoma. According to the Dutch GP guideline (NHG) on amenorrhea, prolactin is mainly meaningful with milk discharge, headache or visual field symptoms, and with absent periods lasting longer than a year without explanation.

What can affect the result?

Stress and pain around the blood draw, a meal, breast or nipple stimulation, sex and intensive exercise shortly before temporarily raise the value; a blood draw at rest, fasting and at least an hour after getting up is the most reliable.
Medicines: antipsychotics, metoclopramide, domperidone, some antidepressants, estrogens and opioids raise prolactin; dopamine agonists and levodopa lower it.
An underactive thyroid and reduced kidney function raise prolactin; a raised value is therefore often assessed together with TSH and creatinine.
Macroprolactin (a harmless bound form) gives a falsely raised result; with a raised value without symptoms, the laboratory can check for this.

Preparation

Have your blood taken in the morning, at least 1 hour after getting up.
Take it easy: stress and heavy exercise shortly before the sample is taken raise prolactin.
Do you take biotin (vitamin B8, often in hair and nail supplements)? Stop at least 2 days before the sample is taken, or 4 days for a high dose.

Who it is for

Who is the test useful for?

Useful for

Useful with absent or irregular periods without explanation, with milk discharge outside breastfeeding, with infertility, in men with repeatedly low testosterone or erection problems with less interest in sex, and with headache with visual field symptoms. Also when taking antipsychotics with symptoms that fit a high prolactin. In people without these symptoms, the result says little; a chance finding of a slightly raised value often leads to unnecessary further tests.

How common is it?

A slightly raised prolactin is a common, usually harmless finding. A prolactinoma is rarer: in the Netherlands the diagnosis is made in about 500 to 700 people a year, mainly in women between 20 and 40. It is, however, the most common hormone-producing tumor of the pituitary gland.

Maastricht UMC+, Department of Endocrinology

Drawbacks and risks

A slightly raised value due to stress or medicines can wrongly lead to fear of a brain tumor and to an unnecessary MRI.
An MRI after a slightly raised value sometimes finds a small, harmless pituitary abnormality that has nothing to do with the symptoms but does lead to years of check-ups.

Get tested

Prolactin: test panels

Prolactin is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
Prolactin
Prolactin; hyper- or hypoprolactinemia.
€ 32,00
Fingerstick
Prolactin
Prolactin; hyper- or hypoprolactinemia.
€ 32,00
Blood draw
Testosterone Replacement Therapy (TRT)
Testosterone, LH, FSH, Oestradiol, Prolactin, liver function, and blood values. For men with low testosterone or TRT monitoring.
€ 175,00
Blood draw
Female Hormones Blood Test
Estradiol, FSH, LH, prolactin, and progesterone. For women with infertility, menstrual disorders, or menopausal symptoms.
€ 179,00
Blood draw
Expanded: Testosterone Replacement Therapy (TRT)
Testosterone, LH, FSH, estradiol, prolactin, blood values, complete liver function, kidney function, and lipid profile.
€ 235,00
Blood draw
Supplemental: Testosterone Replacement Therapy (TRT)
Complete hormonal analysis with testosterone, DHEA-S, thyroid, blood count, liver function, kidney function, lipids, glucose, HbA1c, insulin, hs-CRP, vitamin D and ferritin.
€ 335,00

How reliable is the test?

Prolactin

Prolactin: what is measured?

What can it detect?

What does the result mean?

Prolactin too high

Prolactin too low

After an abnormal result

How reliable is the test?

What can affect the result?

Preparation

Who is the test useful for?

Useful for

How common is it?

Drawbacks and risks

Prolactin: test panels

Prolactin

Prolactin

Testosterone Replacement Therapy (TRT)

Female Hormones Blood Test

Expanded: Testosterone Replacement Therapy (TRT)

Supplemental: Testosterone Replacement Therapy (TRT)

Sources

Other tests: Hormones

Prolactin

Prolactin: what is measured?

What can it detect?

What does the result mean?

Prolactin too high

Prolactin too low

After an abnormal result

How reliable is the test?

What can affect the result?

Preparation

Who is the test useful for?

Useful for

How common is it?

Drawbacks and risks

Prolactin: test panels

Prolactin

Prolactin

Testosterone Replacement Therapy (TRT)

Female Hormones Blood Test

Expanded: Testosterone Replacement Therapy (TRT)

Supplemental: Testosterone Replacement Therapy (TRT)

Sources

Other tests: Hormones