Overview
Prolactin is one of the pituitary stress hormones, like ACTH and TSH, and chronic elevation does substantial damage. It is the hormone of lactation in humans and the "molting hormone" in birds, but it also regulates practically every cell in the body, and it rises steadily with aging in both men and women. High prolactin causes hair loss, bone loss, unwanted lactation in women who are not pregnant, gynecomastia in men, hirsutism in women, infertility, and erectile dysfunction even when testosterone reads normal. Thyrotropin-releasing hormone drives both TSH and prolactin, which is why low thyroid produces high prolactin almost as a rule, and why correcting thyroid function is the most reliable way to bring prolactin down. Lab "normal" ranges have been quietly raised over the decades to accommodate a chronically stressed population; the actual healthy range is 4 to 7 for men and around 12 (maximum) for women.
Key Points
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Prolactin is a pituitary stress hormone that rises with stress, low thyroid, low blood sugar, and aging. It responds to many of the same triggers as ACTH and TSH, and the thyrotropin-releasing hormone activates prolactin release alongside TSH. Hypoglycemia and disturbed oxygen availability during the night both increase prolactin and growth hormone. The pituitary's job is to organise an adaptive stress response, but its hormones are all harmful when they are chronically elevated, and prolactin is one of the indicators of how stressed the whole system has become.
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The actual healthy range is far below what current labs call normal. In the 1970s the healthy upper limit for women was set at around 12 and for men at 4 to 7. Lab ceilings have since been raised to roughly 25 to 30 for women and 18 to 20 for men, but this reflects a stressed population rather than any biological change in what is healthy. A prolactin of 18 or 20 is not reassuring, and men who measured close to 20 within the lab "normal" range consistently had developing breasts.
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Prolactin is a major cause of bone loss. Cortisol, parathyroid hormone, and prolactin together mobilise calcium out of the bone, and all three are increased by estrogen and serotonin. The popular framing that estrogen prevents osteoporosis runs against the fact that estrogen drives the prolactin, serotonin, cortisol, and PTH that dissolve bone. Hip fracture rates have risen over the decades when estrogen has been most heavily prescribed.
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Prolactin causes hair loss in both sexes. Testosterone makes the hair shaft grow thicker and faster; prolactin terminates the growth cycle. Cortisol and prolactin both rise during stress, and the long-noted association of baldness with heart disease and the earlobe crease tracks the same low-thyroid, high-prolactin, high-cortisol pattern. Both hirsutism (excess facial and body hair in women) and head hair loss are associated with high prolactin, with the difference being whether prolactin is steadily high or surges sharply.
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Estrogen and serotonin are the two main drivers of prolactin elevation. Estrogen directly increases prolactin and also increases serotonin systemically, and serotonin is one of the primary mediators by which estrogen drives prolactin up. Birth control pills with high estrogen doses in the 1960s caused an epidemic of prolactin-secreting pituitary tumors; one hospital reported its annual case count going from about five per year to 300 per year. SSRI antidepressants, by raising serotonin exposure, drive the same cascade and produce premature bone loss.
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Thyroid supplementation is the most reliable way to normalise prolactin. Keep TSH at the lower end of the normal range, and prolactin will usually follow. The TSH typically descends first within two or three weeks of adequate thyroid, and prolactin falls more slowly behind it. About a hundred women whose only complaint was chronic unwanted lactation turned out to be hypothyroid, and correcting thyroid function resolved both the lactation and the menstrual irregularities they had alongside it.
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Vitamin A, Calcium and Vitamin D help to lower prolactin. Vitamin A and calcium specifically inhibit excess prolactin secretion. Vitamin D and calcium are critical because prolactin is a calcium regulator, and supplementing them helps balance the cortisol-PTH-prolactin trio. For confirmed prolactin-secreting pituitary tumors, bromocriptine and cabergoline almost always shrink them, but most "high prolactin" presentations are fixable with thyroid alone.
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High prolactin causes infertility and erectile dysfunction even with "normal" testosterone. Several large human studies show that erectile and ejaculatory problems and infertility persist in men with normal testosterone and DHEA when either prolactin or estradiol is elevated or in the top 25th percentile of the reference range. Fertility is best in men when prolactin is between 4 and 7. In women, the prolactin excess that causes unwanted lactation is almost always paired with menstrual irregularities and reduced fertility.
Notable Quotes
"Don't feel reassured if your prolactin is only 18 or 20 on the test because everything is under stress when it's that high."
[Ray Peat — East West Healing: Estrogen vs Progesterone (March 2011)]
"Both hirsutism and hair loss are associated with high prolactin."
[Ray Peat — KMUD: Hair Loss, Inflammation & Osteoporosis (July 2011)]
"Fertility is best when a man has 4 to 7 (ng/ml)."
[Ray Peat — KMUD: Hair Loss, Inflammation & Osteoporosis (July 2011)]
"The simplest way to normalize prolactin is to normalize your thyroid function."
[Ray Peat — KMUD: Tryptophan (November 2019)]
"There is no case in which prolactin will be elevated and you'll be in good health."
[Georgi Dinkov — How to Utilize and Balance Carbohydrate Intake]
"There was a study with bromocryptine showing full cure of 70% of breast cancer cases. Full cure, full remission. No surgery, no radiation, no chemotherapy."
[Georgi Dinkov — How to Utilize and Balance Carbohydrate Intake]
Important Things To Consider
Current lab reference ranges are not a reassurance. The 1970s ceiling of 12 for women and 7 for men is the better target, even though current labs may flag those numbers as low or normal.
The synthetic estrogen birth control pills of the 1960s caused an epidemic of prolactin-secreting pituitary tumors. The lab reference ranges for prolactin were raised partly in response to the influx of women with elevated prolactin from oral contraceptives, which means the "new normal" is partly an artifact of mass exposure to a known cause of pituitary disease.
Erectile dysfunction can persist with completely normal testosterone if prolactin is elevated. Doctors who test only testosterone and find it normal will miss the actual cause in many cases. Asking for a prolactin and an estradiol along with testosterone gives a much more complete picture, and any prolactin in the top quarter of the reference range is worth treating.
Calcium deficiency is a major and often overlooked cause of elevated prolactin. When dietary calcium runs low, parathyroid hormone rises and drives prolactin up to dissolve bone for calcium. Two grams of calcium daily (about three to four cups of milk) is sufficient for most people. Anything below one gram daily starts triggering the parathyroid-prolactin axis.
Hoppy beer can cause gynecomastia in men through the estrogenic compounds in hops. This raises prolactin via the estrogen-prolactin pathway. The same effect shows up in cultures with very heavy hopped-beer consumption, and it is one of the under-recognised drivers of "man boobs" in middle-aged men.
Bromocriptine and cabergoline are the pharmaceutical options for actual prolactin-secreting tumors. They almost always shrink the tumor and bring prolactin down, but are known to cause fibrosis. Lisuride is a related compound without the fibrotic profile (it is actually anti-fibrotic). Most "high prolactin" presentations are not tumors though, and those resolve with two or three weeks of adequate thyroid plus vitamin A, calcium, and vitamin D, watching the TSH come down first and then the prolactin following more slowly.
Unwanted lactation in non-pregnant, non-nursing women is almost always hypothyroidism. It is often paired with either prolonged or excessive menstruation (menorrhagia) or other menstrual irregularities. The thyroid system overcompensating for poor thyroid hormone production produces both the menstrual problem and the milk secretion together, and correcting thyroid function resolves both at once.
Prolactin rises at night along with the other stress hormones. Low blood sugar from overnight fasting and any disturbance to oxygen availability both push prolactin up. People with chronic high prolactin often benefit from a small carbohydrate snack before bed (a bowl of oatmeal, milk and honey, or similar) and from improving sleep quality and breathing.
Post-orgasm prolactin spikes are normal but should resolve quickly. In a healthy person, prolactin rises sharply after orgasm and falls within hours. In a hypothyroid person whose baseline prolactin is already elevated, it can stay high and produce the cluster of symptoms now called post-SSRI Sexual Dysfunction (PSSD) or post-orgasmic illness syndrome (POIS).
Aromatising anabolic steroids will raise prolactin. Nandrolone, trenbolone, and any 18-carbon estrane-core steroid converts readily to estrogen and pushes prolactin up. Non-aromatisable androgens like DHT actually lower prolactin and are approved in several countries for treating gynecomastia.