Sheehan’s Syndrome – causes, symptoms, diagnosis, treatment, pathology

With Sheehan’s syndrome, also sometimes
called postpartum pituitary gland necrosis, “postpartum” refers to the time after
a mother gives birth to an infant, “pituitary gland” refers to a tiny gland that is at
the base of the brain, and “necrosis” refers to death. So, postpartum pituitary gland necrosis is
a disorder where cells in a pituitary gland of a new mother start to die – most commonly
because excess blood loss during childbirth leaves those cells without adequate blood
flow. It is a rare type of pituitary apoplexy. During pregnancy, a group of cells in the
pituitary gland called lactotrophs start to increase in size and number. These lactotrophs secrete the hormone prolactin,
and the increased levels of prolactin prepares the mammary glands to produce milk. Even though there are more lactotrophs that
are larger and more metabolically active, the blood supply to the pituitary gland remains
the same. So there is an increased blood demand without
an increase in supply, making the lactotrophs hypoperfused. In other words, the lactotrophs are just barely
getting enough oxygenated blood, and they will become ischemic and die if blood flow
is reduced further. Since there are more metabolically active
lactotrophs around, they take up a larger proportion of the blood that supplies the
pituitary gland, this increases the risk of ischemia in other cells of the pituitary as
well. During the delivery of an infant, some mothers
can experience excessive blood loss, which is called postpartum hemorrhage. Postpartum hemorrhage is generally defined
as losing more than 500ml of blood after a vaginal delivery or more than 1000ml of blood
after a cesarean section delivery. When this happens, there’s less blood flowing
to the cells in the pituitary gland. Coupled with the increased demand for blood
by the lactotrophs, the pituitary cells no longer receive enough oxygen to survive – resulting
in ischemic necrosis. If blood flow isn’t restored soon, more and
more cells in the pituitary die, and the pituitary gland progressively shrinks, becomes scarred,
and stops producing enough of one or more of hormones. In severe cases, severe destruction and scarring
can lead to an empty sella turcica which is when the pituitary gland shrinks and flattens
into the skull. Increased cell death within the pituitary
also means that a number of hormone levels start to fall. This includes growth hormone, adrenocorticotropic
hormone which acts on the adrenal gland, thyroid stimulating hormone which acts on the thyroid,
and the gonadotropins, luteinizing hormone, and follicle stimulating hormone, which act
on the ovaries. Sheehan’s syndrome results in hypopituitarism
– a deficiency of the pituitary gland – and the symptoms are all related to a decrease
in various pituitary hormones. A classic early symptom of Sheehan’s syndrome
is agalactorrhea, which is not being able to make as much breastmilk or none at all,
because of a lack of prolactin. Later symptoms include amenorrhea, an absence
of a normal menstrual cycle, even after a period of lactation, which is due to a lack
of luteinizing hormone and follicle stimulating hormone. Sheehan syndrome can also cause hypothyroidism,
which can cause a low blood pressure, cold intolerance, and weight gain. It can also lead to low adrenocorticotropic
hormone levels and subsequent adrenal gland insufficiency causing a decrease in sodium
and blood glucose levels. Low growth hormone can lead to fatigue and
loss of muscle mass. In some women, the damage to the pituitary
is relatively mild so they have relatively normal levels of prolactin and don’t have
trouble with breastfeeding, and instead might notice the other symptoms months to years
after the delivery. Sheehan’s syndrome is typically diagnosed
by measuring the pituitary hormones levels – which usually fall depending on the severity
of the ischemic necrosis. In addition, MRI and CT scans can show ring
enhancement or halo around a partially or completely empty sella turcica, called the
‘pituitary ring sign’. Sheehan’s syndrome can be treated by replacing
the deficient hormones, and typically they’re needed for a person’s entire life. All right, as a quick recap, in pregnancy
the pituitary cells are getting just enough blood to survive because the lactotrophs increase
in size and number, taking up more blood than usual. In Sheehan’s syndrome, postpartum hemorrhage
causes lactotrophs and other cells of the pituitary to die, resulting in low levels
of prolactin, growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, luteinizing
hormone, and follicle stimulating hormone. An early symptom is agalactorrhea, whereas
late symptoms include amenorrhea, low blood pressure, low blood sodium, low blood glucose
levels, as well as fatigue and muscle loss.