Sheehan syndrome is a rare condition that affects the pituitary gland, resulting in decreased function following severe blood loss during or immediately after childbirth. The syndrome is also known as postpartum pituitary gland necrosis, reflecting the cell death that occurs within the gland. This damage leads to the pituitary gland’s inability to produce sufficient hormones necessary for regulating various body functions. The resulting deficiency of these hormones causes the wide array of symptoms associated with Sheehan syndrome.
The Critical Link Between Childbirth and Pituitary Damage
The underlying cause of Sheehan syndrome is a lack of oxygen reaching the pituitary gland, typically following a severe postpartum hemorrhage (PPH). During pregnancy, the pituitary gland naturally enlarges, sometimes doubling in size, in preparation for increased hormone production. This physiological change increases the gland’s metabolic demand, making it vulnerable to changes in blood supply.
Severe blood loss or a drastic drop in blood pressure during delivery, known as hypovolemic shock, drastically reduces blood flow to the enlarged pituitary gland. The anterior lobe is particularly susceptible because it is supplied by a low-pressure portal venous system. This lack of blood flow starves the tissue of oxygen, leading to ischemic necrosis.
The extent of the damage determines which hormones are affected and the severity of the symptoms. The resulting damage causes a partial or complete failure of the pituitary gland to release its hormones, a condition called hypopituitarism.
Recognizing the Symptoms of Hormone Deficiency
The clinical manifestations of Sheehan syndrome arise from the loss of pituitary hormones and can present acutely or gradually over months or years. One of the earliest and most common signs is the failure to lactate due to a deficiency in prolactin. A woman may also experience the absence of her menstrual period (amenorrhea) or irregular periods following delivery, linked to a lack of gonadotropins (FSH and LH).
Symptoms that develop more chronically relate to deficiencies in hormones that regulate other endocrine glands. A lack of Thyroid-Stimulating Hormone (TSH) leads to secondary hypothyroidism, manifesting as fatigue, intolerance to cold, weight gain, and slowed thinking. Deficiency of Adrenocorticotropic Hormone (ACTH) results in low levels of cortisol, causing symptoms like low blood pressure, weakness, and fatigue.
The loss of ACTH is serious, as it can lead to an adrenal crisis—a life-threatening state of dangerously low blood pressure and hypoglycemia under stress. Other signs of chronic deficiency include loss of pubic and underarm hair, decreased sex drive, and dry skin. Growth hormone deficiency is also common, contributing to low energy and changes in body composition.
How Sheehan Syndrome is Diagnosed
Diagnosing Sheehan syndrome often begins with a detailed review of the patient’s medical history, focusing on significant blood loss and complications during childbirth. Characteristic initial signs, such as difficulty breastfeeding and the absence of menstruation after delivery, provide important clues. The challenge is that many symptoms, such as fatigue and mood changes, can be mistaken for general postpartum issues.
Laboratory tests are essential for confirming the diagnosis by measuring basal hormone levels in the blood. Doctors check for low levels of pituitary hormones, including prolactin, TSH, ACTH, and the gonadotropins FSH/LH. If basal levels are inconclusive, dynamic stimulation tests may be performed to assess the pituitary reserve. These tests involve administering a stimulating hormone and then measuring the pituitary gland’s response, revealing whether it can still produce hormones effectively.
Imaging studies are also used to visualize the pituitary gland and surrounding structures. Magnetic Resonance Imaging (MRI) is the standard imaging method, showing changes in the size and structure of the gland. In chronic cases, MRI may reveal atrophy or scarring, sometimes showing an “empty sella,” which is indicative of tissue necrosis.
Lifelong Management Through Hormone Replacement
Treatment for Sheehan syndrome centers on lifelong Hormone Replacement Therapy (HRT) to substitute the hormones the damaged pituitary gland can no longer produce. The goal is to restore normal hormone levels, alleviate symptoms, and prevent life-threatening complications. The specific regimen is tailored to the individual patient based on their hormone deficiencies.
Glucocorticoids, such as hydrocortisone or prednisone, replace the deficient cortisol resulting from ACTH loss. This replacement manages the body’s stress response and maintains blood pressure and blood sugar levels. Patients must increase their glucocorticoid dose during periods of stress, such as illness, injury, or surgery, to prevent an adrenal crisis.
Thyroid hormone replacement, typically with levothyroxine, compensates for the lack of TSH, regulating metabolism and energy levels. Sex hormones, including estrogen and progesterone, are replaced to regulate menstrual cycles and manage symptoms of premature menopause. With diligent adherence to HRT and regular monitoring by an endocrinologist, individuals with Sheehan syndrome lead healthy, normal lives.