HORMONAL DISORDERS
HYPERPROLACTINEMIA
Hyperprolactinemia is a condition in which the pituitary gland produces too much prolactin - the hormone that is responsible for milk production in breastfeeding women. Low levels of prolactin are normal in non-breastfeeding women (approximately 15-25 ng/mL) and even men (as low as 5 ng/mL). During breast feeding, prolactin levels increase exponentially (to levels as high as 35-600 ng/mL). However, when prolactin levels are chronically elevated outside of breast feeding periods, this condition is called hyperprolactinemia. With a prevalence of less than 1%, it is a relatively rare condition, which can affect both women and men. Hyperprolactinemia can have several causes, such as (benign) pituitary tumors (such as prolactinomas) or chemical imbalances (such as dopamine insufficiency). Symptoms of hyperprolactinemia include milky nipple discharge (galactorrhea), decreased levels of sex hormones (estrogen and testosterone), loss of bone density, decreased libido, and infertility (as well as irregular menstrual cycles and vaginal dryness in women, and erectile dysfunction and gynecomastia in men). Hyperprolactinemia is diagnosed with a physical exam, blood work, and imaging (such as MRI, to confirm possible tumors). It can be treated with drug therapy (mainly dopamine agonists, which reduce prolactin production) and - in the case of pituitary tumors - surgery or radiation.
Causes
While several factors can contribute to an excess production of prolactin in the pituitary gland, there are two major causes for hyperprolactinemia.
One reason for hyperprolactinemia can be pituitary tumors (which are mostly benign, called adenomas). The pituitary is a small structure at the base of the brain, which - upon stimulation from the hypothalamus - is the main locus of production for many hormones in the body. Pituitary tumors, therefore, can be either hormone-producing (i.e. "functioning", for instance tumors derived from glandular tissue) or not hormone-producing (i.e. "non-functioning"). One such functioning tumor is the prolactinoma. The glandular tissue in prolactinomas is usually mono hormonal, which means that it only produces prolactin, thereby causing the excess prolactin present in hyperprolactinemia.
Another reason for hyperprolactinemia can be chemical imbalances in the body. For instance, the pituitary can be induced to produce an excess of prolactin when there is insufficient dopamine in the body (dopamine is a neurotransmitter involved, amongst other things, in brain mechanisms underlying reward and learning). Dopamine insufficiency can be the result of certain disorders (such as Parkinson's disease) or medications (such as some neuroleptics and other psychiatric drugs).
Symptoms
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In women and men: Milky nipple discharge (galactorrhea), decreased levels of sex hormones (estrogen and testosterone), loss of bone density, decreased libido (sex drive), and infertility
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In women only: Irregular menstrual cycles (even amenorrhoea) and vaginal dryness (sometimes causing pain during sexual intercourse, dyspareunia)
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In men only: Erectile dysfunction and gynecomastia (growth of female-looking breasts)
Diagnosis
Due to its distinct symptoms (lactation when not breastfeeding), hyperprolactinemia is usually diagnosed by taking a patient's history (and performing a physical exam). Blood tests can then be used to confirm elevated prolactin levels in the blood. If this is the case, imaging (such as an MRI) will also likely be performed to determine whether there is a tumor present in the pituitary.
Treatments
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Drug therapy: If the hyperprolactinemia is caused by chemical imbalances, such as
dopamine insufficiency, drug therapy can be an effective and sufficient treatment. For instance, if dopamine insufficiency is present, dopamine agonists can be given (or dopamine-reducing medication can be discontinued, if this does not cause other issues). Such medications include cabergoline (a dopamine promoter, e.g. Dostinex) and bromocriptine (a dopamine receptor agonist, e.g. Parlodel or Cycloset). Dopamine inhibits production of prolactin by the pituitary, thereby mediating the symptoms of hyperprolactinemia. - Surgery or radiation: If tumors are the cause of hyperprolactinemia, a surgery may be necessary to remove them from the pituitary (to stop overproduction of prolactin and other hormones and avoid excessive compression of the pituitary gland and other local structures). However, because of the location of the pituitary at the base of the brain, where surgical access can be difficult (it is often done transnasal, i.e. through the nose), radiation may be suggested as alternative to surgery in some cases.