Does Elevated Prolactin Play a Role in Recurrent Miscarriages?

Could Nature's Contraception Also Cause Miscarriages?

The mammalian pituitary gland, showing the anterior lobe (adenohypophysis) and posterior lobe
The mammalian pituitary gland, showing the anterior lobe (adenohypophysis) and posterior lobe. Getty Images/Encyclopaedia Britannica/UIG

As you are probably aware if you are researching miscarriage causes, doctors cannot always explain why miscarriages happen. Even cases of recurrent miscarriages have an identifiable cause only about half the time. There are many theories about what causes the other half of recurrent miscarriage cases, but few are conclusively proven. One theory that falls in the latter category is the idea that high levels of a hormone called prolactin might cause miscarriages.

What Is Prolactin?

Prolactin is a hormone produced primarily by the anterior pituitary, a pea-sized gland at the base of the brain. Prolactin gets its name because it plays a major role in inducing milk production in lactating women, but prolactin also plays many other roles in the body, including in the immune system.

Prolactin is a hormone produced primarily by the anterior pituitary, a pea-sized gland at the base of the brain. Prolactin gets its name because it plays a major role in inducing milk production in lactating women, but prolactin also plays many other roles in the body, including in the immune system.

When prolactin levels are elevated, the condition is labeled hyperprolactinemia. Symptoms of hyperprolactinemia can include menstrual problems, lactation in women who are not breastfeeding, and infertility, though not all women have symptoms.

The most common cause of hyperprolactinemia is a non-cancerous pituitary tumor called an adenoma, but the condition can also occur in some people with hypothyroidism.

Prolactin can also be elevated in response to environmental triggers, such as exercise or stress, and in people who take medications that affect the brain chemical dopamine.

What Role Does Prolactin Play in Fertility?

During lactation, which follows birth, prolactin levels are significantly elevated.

Some have theorized that As one might expect, levels of this hormone are markedly elevated during periods of lactation. Because menstruation and the normal ovulatory cycle often ceases during lactation, prolactin acts as a natural contraceptive that protects against back-to-back pregnancies.

According to this well-accepted theory, women with elevated prolactin levels who are trying to conceive may experience menstrual and ovulatory cycles that are irregular, making it more difficult to become pregnant. When it comes to prolactin and recurrent miscarriages, however, the jury is still out. A few studies have found elevated prolactin levels in women with recurrent miscarriages. What this finding means, however, is controversial. Some people feel that elevated prolactin may cause miscarriages, while others feel that it is too early to say so definitively.

In Support of the Theory

Given the interworking of so many different hormones in the human body, it's feasible that an imbalance could cause numerous problems. It's clear that hyperprolactinemia can cause infertility, and doctors often treat high prolactin levels in women having trouble conceiving.

In the case of recurrent miscarriages and prolactin, one 1998 study found elevated prolactin levels in women who had multiple pregnancy losses and improvements in pregnancy outcome after treating the elevated prolactin.

The findings have not been verified in a large scale study, but because the treatment is thought to be safe, some doctors test for and treat elevated prolactin when testing women for causes of recurrent miscarriages -- similar to in women suffering infertility.

In Opposition of the Theory

The studies that have found a link between high prolactin levels and miscarriage were not large enough to be conclusive.

In addition, researchers still do not fully understand the functioning of prolactin in the body, and many feel that it is too early to say whether or not the elevated prolactin levels in women with miscarriages have any clinical relevance. Other factors could theoretically account for higher prolactin levels in women with miscarriages, so many doctors prefer to wait for more evidence before considering prolactin as a cause of recurrent miscarriages.

Where It Stands

Some doctors regularly test prolactin in couples with recurrent miscarriages and prescribe medications, such as bromocriptine or cabergoline, to reduce the prolactin levels.

These medications appear to be safe to use during pregnancy and are commonly used for women with infertility from hyperprolactinemia. But right now, there are no formal recommendations to test for and treat prolactin in women with recurrent miscarriages.

Sources:

Colao, Annamaria, Roger Abs, David Gonzalez Barcena, Phillipe Chanson, Wolfgang Paulus, and David Kleinberg, "Pregnancy outcomes following cabergoline treatment: extended results from a 12-year observational study." Clinical Endocrinology Jan 2008. Accessed 20 Apr 2008.

Freeman, Marc E., Bela Kanyiecska, Anna Lerant, and Gyorgy Nagy, "Prolactin: Structure, Function, and Regulation of Secretion." Physiological Reviews Oct 2000. Accessed 20 Apr 2008.

Gurbuz, B., S. Yalti, C. Ficicioglu, S. Ozden, G. Yildirim, and C. Sayar, "Basal hormone levels in women with recurrent pregnancy loss." Gynecological Endocrinology Aug 2003. Accessed 20 Apr 2008.

Hirahara, F., N. Andoh, K. Sawai, T. Hirabuki, T.Uemura, and H. Minaguchi, "Hyperprolactinemic recurrent miscarriage and results of randomized bromocriptine treatment trials." Fertility and Sterility Aug 1998. Accessed 20 Apr 2008.

Rossi, A.M., S. Vilska, P.K. Heinonen, "Outcome of pregnancies in women with treated or untreated hyperprolactinemia. European Journal of Obstetrics and Gynecology and Reproductive Biology Dec 1995. Accessed 20 Apr 2008.

Serri, Omar, Constance L. Chik, Ehud Ur, and Shereen Ezzat, "Diagnosis and management of hyperprolactinemia." Canadian Medical Association Journal 16 Sept 2003. Accessed 20 Apr 2008.

Sonino, N. C. Navarrini, C. Ruini, F. Fallo, M. Boscaro, and G.A. Fava, "Life events in the pathogenesis of hyperprolactinemia." European Journal of Endocrinology Jul 2004. Accessed 20 Apr 2008.

Wand, Gary S. "Diagnosis and Management of Hyperprolactinemia." Jan 2003. Accessed 20 Apr 2008.

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