Hypoprolactinemia

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Introduction0:00–0:16

With hypoprolactinemia, hypo- means below, -prolactin refers to the hormone produced by the pituitary gland, and -emia refers to the blood, so hypoprolactinemia means lower than normal prolactin levels in the blood.

Physiology0:16–2:10

Normally, at the base of the brain, there’s a small pea-sized gland called the pituitary gland. The anterior pituitary - which is the front of the pituitary gland - has a number of different cells, each of which secrete a different hormone.
One group, the lactotroph cells, secrete prolactin. In men, prolactin decreases testosterone production.
In women, during pregnancy, elevated levels of estrogen stimulate the lactotroph cells 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 starts - 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, as well as in men, prolactin levels are usually kept in check by the hypothalamus in two ways.
The first way is the most important, and it’s when the hypothalamus secretes a constant stream of dopamine which in this setting is called prolactin inhibiting factor.
Dopamine binds to specific receptors on the lactotroph cells and inhibit the release of prolactin. The second way is less significant, and it’s when the hypothalamus secretes thyrotropin releasing hormone, also called prolactin releasing hormone, which can stimulate prolactin release.
If the level of prolactin rises for any reason, then it signals the hypothalamus to release more dopamine, eventually decreasing its own production, a process called negative feedback or feedback inhibition.

Causes2:10–3:05

The most common cause of hypoprolactinemia is Sheehan’s syndrome, a disorder where lactotroph cells die in a woman that has recently given birth and has postpartum hemorrhage - excessive blood loss during delivery.
That happens because the lactotroph cells have an increased demand for blood, and the postpartum hemorrhage results in a decreased supply of blood - that leads to ischemia and necrosis.
Another cause of hypoprolactinemia is taking medications containing dopamine, as well as dopamine agonists like bromocriptine which inhibit prolactin release from lactotroph cells.
Another cause is a tumor in the pituitary gland or hypothalamus, which puts pressure on the nearby lactotroph cells and interferes with their ability to produce prolactin.
That happens in part because the tumor creates local inflammation that can damage the lactotroph cells. Hypoprolactinemia generally only causes symptoms in breastfeeding women who can have agalactorrhea, which is a decrease in breastmilk production.

Symptoms3:05–3:21

In women that aren’t breastfeeding, and in men, hypoprolactinemia doesn’t usually cause symptoms. The diagnosis of hypoprolactinemia can be made when there are decreased levels of prolactin in the blood, particularly if the levels of prolactin are low in spite of receiving thyrotropin-releasing hormone.

Diagnosis3:21–3:40

An MRI can help confirm the Sheehan's syndrome or the presence of a pituitary or hypothalamic tumor. Treatment is usually reserved for women who want to breastfeed.

Treatment3:40–3:55

Dopamine antagonists can be used to oppose the action of dopamine and that removes the inhibition on the lactotroph cells.
If there’s a tumor, though, surgery may be needed. All right, as a quick recap, hypoprolactinemia, or low prolactin levels in the blood, is most often caused by Sheehan’s syndrome, where lactotroph cells die in women who have postpartum hemorrhage.

Review3:55–4:12

These women can develop agalactorrhea and can be treated with dopamine antagonists.