Sheehan syndrome

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.

The pituitary gland sits in a small space at the base of the brain called the sella turcica, 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; prolactin, which stimulates mammary glands to produce milk; as well as follicle-stimulating hormone and luteinizing hormone, which control 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 antidiuretic 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.

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, starts 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. 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 sella turcica.

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.