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Endocrine system




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A 32-year-old man comes to his outpatient provider because of headaches that began five-months ago. The patient reports that the headaches are worse in the morning and improve over the day. In addition, the patient endorses reduced body hair. He does not use any medications. Temperature is 37.4°C (99.3°F), pulse is 68/min, respirations are 20/min, and blood pressure is 125/72 mmHg. Physical exam is notable for restricted peripheral vision and white watery discharge from the nipples. Further review of the patient’s history will most likely reveal which of the following findings?

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Hyperprolactinemia p. 250, 334, 544

anovulation p. 669

calcium channel blockers and p. 325

risperidone and p. 597


With hyperprolactinemia, hyper- means above, -prolactin refers to the hormone produced by the pituitary gland, and -emia refers to the blood, so hyperprolactinemia means higher than normal prolactin levels in the blood.

Normally, at the base of the brain, there’s a small pea-sized gland called the pituitary gland.

The anterior pituitary - the front of the pituitary gland - has a number of different cells, each of which secretes a different hormone.

One group, the lactotroph cells, secrete prolactin. In men, excess prolactin decreases testosterone production.

In women, during pregnancy, elevated levels of estrogen stimulate the lactotrophs to produce large amounts of prolactin which stimulates alveolar cells in the breasts.

In response to prolactin, the alveolar cells divide and enlarge - and once a baby is born, lactogenesis begins - which means that milk is produced.

Apart from milk production, high levels of prolactin also inhibit the release of gonadotropin releasing hormone from the hypothalamus, which results in decreased luteinizing and follicle stimulating hormone levels, which in turn, decreases estrogen levels.

In women, this can stop ovulation and menstruation, which is why women typically don’t have a menstrual period while breastfeeding. In women that are not pregnant or breastfeeding, and in men, prolactin levels are usually kept in check by the hypothalamus in two ways.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
  5. "Laboratory and clinical significance of macroprolactinemia in women with hyperprolactinemia" Taiwanese Journal of Obstetrics and Gynecology (2017)
  6. "Pitfalls in the Diagnostic Evaluation of Hyperprolactinemia" Neuroendocrinology (2019)

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