Prolactin: the hormone that can quietly switch off testosterone and sperm
Prolactin is produced by the pituitary gland and is best known for its role in breast milk, but men make it too, and when it runs high it suppresses the hormones that drive the testicles. It is an easily overlooked and very treatable cause of low testosterone, low libido and a poor semen analysis. Prolactin is a blood test a urologist or primary-care doctor orders, usually alongside testosterone and LH when those are low.
What your number means
| Normal | under 20 ng/mL | Prolactin is not contributing to a hormone or fertility problem. A value near the upper limit after a stressful or difficult blood draw is usually not meaningful. |
|---|---|---|
| Mildly high | 20–50 ng/mL | Frequently caused by medications, stress, a recent meal, exercise or the venipuncture itself. Should be repeated on a calm morning before anything else is done. If persistent, medication review and a check for a small pituitary adenoma follow. |
| High | 50–200 ng/mL | Less likely to be an artifact. A specialist will review medications and usually arrange pituitary MRI, since a prolactin-secreting adenoma (prolactinoma) becomes more likely as the level rises. |
| Very high | above 200 ng/mL | Strongly suggests a prolactinoma. These are benign and respond well to medication, which restores testosterone and sperm production in most men. |
What it measures
Prolactin is secreted by lactotroph cells in the anterior pituitary. Unlike most pituitary hormones, its main control is inhibitory: dopamine from the hypothalamus constantly holds it down. Anything that reduces dopamine signalling, or physically interrupts the connection between hypothalamus and pituitary, lets prolactin rise.
Levels are pulsatile and rise with sleep, stress, pain, exercise, sexual activity, nipple stimulation and eating. The stress of a difficult blood draw alone can push prolactin above the reference limit. For that reason a mildly elevated result is repeated, ideally in the morning after resting quietly for 20 to 30 minutes, before it is treated as real.
Some men carry a harmless form called macroprolactin, a large antibody-bound version that reads high on the assay but is biologically inactive. If prolactin is elevated without any symptoms, a doctor may ask the lab to screen for it.
Why it matters for sperm production
High prolactin suppresses the release of GnRH from the hypothalamus, which in turn reduces LH and FSH from the pituitary. The testicles receive less signal, testosterone falls, and sperm production declines. This is secondary hypogonadism with a specific and fixable cause.
The symptoms often show up before the semen analysis does. Loss of libido, erectile difficulty, fatigue and, less commonly, breast tenderness or milk production are classic. Because reduced sexual function directly affects the chance of conception, prolactin matters for fertility on two fronts.
Prolactin does not need to be dramatically high to matter. Levels in the 30 to 50 ng/mL range from medication use can be enough to lower testosterone and LH in some men. The pattern of low testosterone, low or inappropriately normal LH, and elevated prolactin is what a doctor is looking for.
What raises or lowers it
Medications are the most common cause of elevated prolactin in men. Antipsychotics, particularly risperidone and haloperidol, are the strongest offenders because they block dopamine directly. SSRIs and other antidepressants, metoclopramide and domperidone, some blood pressure medications such as verapamil and methyldopa, opioids and H2 blockers can all raise it.
Prolactinomas, benign tumours of the pituitary lactotrophs, are the most important cause to identify. Small ones (microadenomas) are common and often produce only moderately raised levels; larger ones can produce very high values and may cause headaches or vision changes by pressing on nearby structures. Other pituitary or hypothalamic conditions raise prolactin by interrupting the dopamine supply.
Underactive thyroid raises prolactin, because the thyroid-releasing hormone that goes up in hypothyroidism also stimulates lactotrophs. Chronic kidney disease and liver cirrhosis reduce clearance. Stress, poor sleep, chest wall injury and heavy exercise raise it temporarily. There is no common reason for prolactin to be low, and low values are not a fertility concern.
What your doctor may do about it
The first step is confirming the result with a repeat draw under calm conditions and reviewing every medication and supplement. If a medication is the likely cause, a doctor may discuss alternatives with whoever prescribed it; stopping a psychiatric medication without guidance is never recommended. Thyroid function and kidney function are usually checked in the same panel.
If prolactin stays elevated without an obvious cause, or is above roughly 50 ng/mL, an endocrinologist will usually arrange an MRI of the pituitary. If a prolactinoma is found, first-line treatment is a dopamine agonist such as cabergoline, which shrinks the tumour and normalises prolactin in most men. Testosterone, libido and sperm production commonly recover over the following months. Surgery is reserved for the minority who do not respond or cannot tolerate medication.
Because the fix is targeted and effective, prolactin is one of the few abnormal hormone results in male fertility where treatment reliably improves the semen analysis. It is also why prolactin should be part of the workup whenever testosterone and LH are both low.
When to retest
Any mildly elevated prolactin should be repeated on a separate morning, after resting quietly and without a recent meal or exercise, before imaging or treatment is considered. Two elevated values are needed to call it hyperprolactinemia.
On a dopamine agonist, an endocrinologist typically rechecks prolactin within 4 to 8 weeks, then periodically, together with testosterone. A semen analysis at about 3 months after prolactin normalises shows whether sperm production has responded, since a production cycle takes around 74 days.
If a medication was changed, recheck prolactin and testosterone after 6 to 8 weeks. Prolactin is not part of a routine fertility screen when testosterone is normal; Hera's semen analysis is usually the first step, and prolactin is added when low testosterone, low LH or symptoms point to it.
Common questions
What is a normal prolactin level for men?
Most laboratories set the upper limit for men between 15 and 20 ng/mL, though it varies by assay. Values slightly above that are common after a stressful blood draw, a meal, exercise or poor sleep, and are repeated before they are taken seriously. Values above about 50 ng/mL are more likely to reflect a medication effect or a pituitary adenoma.
Can high prolactin cause infertility in men?
Yes. High prolactin suppresses GnRH, LH and FSH, which lowers testosterone and sperm production and often reduces libido and erectile function. The good news is that it is one of the most treatable hormonal causes of male infertility: addressing the medication or treating a prolactinoma usually restores testosterone and improves the semen analysis within months.
Which medications raise prolactin?
Antipsychotics such as risperidone and haloperidol are the strongest, followed by SSRIs and other antidepressants, the anti-nausea drugs metoclopramide and domperidone, some blood pressure medicines including verapamil and methyldopa, opioids and H2 blockers. Do not stop a prescribed medication on your own; ask the prescribing doctor whether an alternative is suitable.
Does high prolactin mean I have a brain tumour?
Usually not. Most elevated prolactin results in men come from medications, stress, thyroid problems or the blood draw itself. When the level is persistently high without an explanation, or above about 50 ng/mL, a doctor will image the pituitary. Prolactinomas are benign, common, and respond to medication in the great majority of cases.