Prolactinemia is a fairly common cause of hypogonadism so we’ve written up a little primer about what it is and how it can impact your fertility. In most cases prolactinemia means hyperprolactinemia: an excess of prolactin released into your bloodstream. It is a common and reversible cause of male infertility accounting for about 11% of men whose sperm concentration is low.
What prolactin does for men
Prolactin is a hormone produced in your pituitary gland, and secreted into your bloodstream. What most people know about prolactin is that in women, it induces lactation after birth and during pregnancy enhances breast enlargement to get ready for breast feeding.
Prolactin is an integral part of everyone’s complex endocrine system, which puts out myriad chemical signals to the body: grow, remain, recede, eat, run, don’t eat, punch, kick, sleep, have sex, have more sex, burn calories, get hard, slow your heart rate, be hairier, secrete, put out signals, don’t put out signals, etc. Prolactin binds to specific receptors in the gonads, lymphoid cells, liver, heart, lungs, thymus, spleen, pancreas, kidney, skeletal muscles, skin, central nervous system, mamillary glands, and female reproductive organs, among other sites.
It not only helps regulate testosterone production in men, but also helps to regulate immune functions, salt and water balances, metabolic functions, endocrine system, brain and behavior, and growth and development. Prolactin is what tells your body that it’s satisfied after sex, and lets the arousal mechanisms (aka dopamine) know they can settle down for a bit.
Because higher levels of prolactin are found in fathers of young children and in expectant fathers, as compared to un-mated males, according to a large-scale study in the Phillipines, behavioral endocrinologists have theorized that a modest rise in prolactin helps prepare men for the task of fatherhood. It quiets the sex drive, they figure, and along with oxytocin—with its weird reputation for being both the “cuddle” hormone as well as a byproduct of stress—helps dads of young children bond to and empathize with their offspring.
What too much prolactin looks like on men
Elevated levels prolactin in the blood signals the gonads to make less testosterone (hypogonadism). This means that hyperprolactemia can indirectly but definitely cause decreased libido, erectile dysfunction, dimished ejaculate volume, and a low concentration of sperm (oligospermia), and enlarged breasts (in men this is called gynaecomastia).
Other sources can cause these problems, but the case of hyperprolactinemia, these symptoms may be subtle or not noticeable in every day life. If you put on a bit of weight, those man boobs might seem like nothing the treadmill can’t fix (until you notice they’re more like rubber than fat); if you’re not trying to conceive, changes in sperm concentrate or ejaculate volume will go undetected; and finally, the loss in the areas of libido and erectile function may happen so gradually as to obscure the problem.
What’s more, sperm quality will be affected first, when through hormone-signaling cascade, high prolactin inhibits release of the gonadotropin-release hormone, which results in turn in decreased release of LH and FSH. Together with decreased testosterone secretion, these decreases cause spermatogenic arrest (interruptions in making sperm so you don’t make as much), impaired sperm motility (your boys can’t swim well enough to reach the egg), and altered sperm quality. More obvious physical symptoms of the hypogonadism, such as gynaecomastia or erectile dysfunction, may not appear until prolactin has been elevated longer.
Rarely, hyperprolactemia may be accompanied by headaches or eye problems.
Diagnostic tools: the trusty blood test
A few caveats. One is that no one agrees on what the right prolactin level is for men, although a blood test could tell you if it’s skyrocketed. A typical prolactin level may range from 2-18 mcg/L but a high prolactin level might be 10-20 times the reference range.
There are some normal fluctuations in this hormone. Your prolactin levels change throughout the day, so the test is usually given between 8 a.m. and 10 a.m.—about three hours after you wake—to establish a consistent reference range.
Sometimes levels also go up during periods of stress, even briefly. And, they go up when your nipples are stimulated—so put those nipple clamps away and keep your sweetie away from your pecs for a day or so before the blood test. Even exercise or a high-protein meal can bump the levels up a bit, but don’t sweat it. Small rises are not likely to be the cause of a big problem.
It can be helpful to look at prolactin levels next to testosterone levels, because ongoing high prolactin secretion will signal the body to lower testosterone production. Your doctor may also repeat the prolactin test to verify an elevation wasn’t a temporary fluctuation, especially if the testosterone level is normal-range.
Prolactin levels through the roof
If the value is very high, then it’s time to look for the cause. Levels in the ballpark of 200 mcg/L may prompt an MRI to look for a tumor in the pituitary gland that actually secretes excess prolactin (called a prolactinoma). Other problems with your pituitary or tumors in its vicinity may cause an unusually high prolactin level. Very large tumors, which are rare, may also press on the neighboring optic chiasm, causing eye problems and headaches.
Your doctor may also review your medication list, as certain medications can raise the level of this hormone—some more than others. Examples include antidepressants, some drugs that treat stomach problems—including PPIs or proton pump inhibitors, many of which are available over the counter—select blood pressure medications, and several antipyschotics. Talk with your prescribing doctor before making any medication changes.
Cocaine use can also raise prolactin. You don’t need to ask your doctor’s permission, pass go, or collect $200—flush the blow if you’re planning to be a dad.
You might also have a high prolactin level if you have an underactive thyroid (hypothyroidism), kidney disease, problems with your thalamus—the area in your brain that gives orders to the pituitary gland—or hypothalamic disease, or trauma to/irritation of the chest wall.
Treatment for hyperprolactemia depends on the cause. Medication-related causes may be solved simply with a doctor-prescribed adjustment in type or dose. For tumors, the treatments generally target shrinking the tumor and limiting its secretion effects with drug therapy (dopamine agonists). Drugs that dampen prolactin production and its release, such as bromocriptine and cabergonline, can lower serum prolactin levels enough to restore male fertility. These regimen normally reduce the size of the prolactinoma as well. In rare and difficult cases of prolactemia-induced male infertility, such as stubborn macroprolactinomas (large tumors), hormone therapy may be added to the normal drug regimen.
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