Sheehan syndrome

Definitions & Key takeaways

Sheehan syndrome, also known as postpartum hypopituitarism, is a condition that affects women who have experienced postpartum hemorrhage (PPH). PPH causes ischemia to lactotrophs and other cells of the pituitary, causing them. This results in deficiencies of prolactin, growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, luteinizing hormone, and follicle-stimulating hormone.

During pregnancy, pituitary cells increase in size and number, taking up more blood than usual. So, when there is PPH, these cells are prone to starve and become ischemic. An early symptom of Sheehan syndrome is agalactorrhea, whereas late symptoms include amenorrhea, low blood pressure, low blood sodium, and glucose levels, fatigue, and muscle loss. Sheehan's syndrome can be treated by replacing the deficient hormones, usually for a person's entire life.

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Introduction0:00–0:35

Sheehan syndrome, also known as postpartum pituitary gland necrosis, was first described in the 1930s by British doctor and pathologist Harold Sheehan.
In postpartum pituitary gland necrosis, postpartum means after childbirth, pituitary gland refers to a small, powerful gland that helps control hormones during pregnancy and beyond, while necrosis means cell death.
So in postpartum pituitary gland necrosis, parts or sometimes the entire pituitary gland can be damaged after childbirth, usually due to severe blood loss during or after delivery.

Physiology0:35–1:27

The pituitary gland sits in a small space at the base of the brain called the cella tersica, and it acts as the body's hormone control center.
The front part, called the anterior pituitary gland, produces growth hormone which helps the body grow, and prolactin, which stimulates mammary glands to produce milk, as well as follicle stimulating hormone and luteinizing hormone which control the menstrual cycle and fertility.
Additionally, the anterior part produces thyroid stimulating hormone, which keeps the metabolism running flawlessly, and adrenocorticotropic hormone, which stimulates the adrenal glands to produce cortisol.
On the other hand, the back part called the posterior pituitary gland, stores and releases two main hormones. One is the anti-diuretic hormone, which controls the water balance in the body, and the second is oxytocin, which plays a key role in labor and contractions of the womb during childbirth.

Pathology1:27–2:43

During pregnancy, the pituitary gland works overtime to support the body through pregnancy and get it ready for childbirth and breastfeeding.
One specific group of cells in the anterior pituitary called lactotrophs start to grow in size and increase in number. These cells are responsible for prolactin production.
As the lactotrophs grow and become more active, the pituitary gland grows, demanding more energy and resources. But here's the catch.
Even though the lactotrophs are growing, working harder, and using more energy, the blood supply to the pituitary gland doesn't increase.
This makes the pituitary gland extremely vulnerable to blood loss. So if there's heavy bleeding during or after delivery, referred to as postpartum hemorrhage, the overall blood volume in the cardiovascular system drops, resulting in hypoperfusion of organs, including the brain and pituitary gland.
When the pituitary gland doesn't get enough blood, it can't get the oxygen and nutrients it needs, especially when it is already larger in size than usual.
And lactotrophs, which are the most active cells, suffer the most. Without enough oxygen and nutrients, they die off, stopping prolactin production.

Symptoms2:43–3:48

This lack of blood flow that results in cell death is also known as ischemic necrosis and mainly affects the anterior pituitary gland.
If the body fails to restore blood flow quickly, damage to the pituitary gland can worsen. Over time, the pituitary gland can shrink and stop producing other hormones.
In the most severe cases, it can become so small that it almost disappears from its spot in the skull. This condition is called empty cellatursica.
Now, switching gears and moving on to clinical manifestations. In rare cases, Sheehan syndrome shows up days or weeks after childbirth.
But more often, signs and symptoms develop slowly over many years, which makes them easy to miss. And based on how much the pituitary gland is damaged, clinical features can vary from mild to severe.
In milder cases, the pituitary gland stops producing just one hormone, which is known as isolated hypopituitarism. Because lactotrophs are first to die off, the gland stops producing prolactin.
With no prolactin, the body cannot trigger mammary glands to produce milk, which results in failure of lactation after delivery.

Diagnosis and treatment3:48–4:16

Sometimes necrosis can damage other cells in the pituitary gland, impairing the production of other hormones. As a result, the body might stop producing the growth hormone, which results in non-specific symptoms such as weakness and fatigue.
Next, without follicle stimulating hormone and luteinizing hormone, the ovaries stop working properly, so periods stop, which is known as amenorrhea.
Also, fertility can become a problem. In severe cases of ischemic necrosis, the pituitary gland stops producing thyroid stimulating hormone, causing thyroid dysfunction and signs of hypothyroidism.

Review4:16–6:45

These include excessive fatigue, dry, brittle hair, cold intolerance, constipation, and weight gain. Less frequently, the pituitary gland loses the ability to produce adrenocorticotropic hormone, and that's when things get more serious.
Without adrenocorticotropic hormone, adrenal glands do not receive the signal to release cortisol, which is a hormone the body needs to deal with stress.
Without it, a person typically experiences weakness, fatigue, nausea, vomiting, and hypoglycemia, or low blood sugar levels.
In severe cases, a person might develop an adrenal crisis, which can result in hypotension and hypovolemic shock. And when the anterior pituitary can no longer produce any of its hormones, the condition is known as pan-hypopituitarism.
The posterior pituitary usually stays safe because it has a better blood supply. However, if the damage is severe enough, the posterior part can stop working too.
When that happens, the body can't release anti-diuretic hormone, which causes the person to lose a lot of water through urine called polyuria and feel extremely thirsty, known as polydipsia.
This condition is called central diabetes insipiditus. To diagnose Sheehan's syndrome, check pituitary hormone levels, which are typically low depending on the extent of gland damage.
Next, review the medical history for past childbirth complicated by severe blood loss, often 7 to 19 years earlier. Also, be sure to order a brain MRI or CT which might show a ring enhancement or halo around a partially or completely empty cellatursica, known as the pituitary ring sign.
Finally, treatment involves lifelong hormone therapy to return hormone levels back to normal and relieve symptoms of either isolated hypopituitarism or pan-hypopituitarism.
All right, as a quick recap, Sheehan syndrome, or postpartum pituitary gland necrosis, occurs when heavy blood loss during or after childbirth severely reduces blood flow to the pituitary gland, causing ischemic necrosis.
This is particularly harmful to the lactotrophs, which are responsible for prolactin production. However, in more severe cases, necrosis can damage other parts of the pituitary gland, which can result in pan-hypopituitarism.