The signs and symptoms of hypopituitarism usually develop gradually and get worse over time. They are sometimes subtle and may be overlooked for months or even years. But for some people, signs and symptoms develop suddenly.

Signs and symptoms of hypopituitarism vary from person to person, depending on which pituitary hormones are affected and to what degree. In people who have more than one pituitary hormone deficiency, the second deficiency may increase or, in some cases, hide the symptoms of the first deficiency.

Growth hormone (GH) deficiency

In children, GH deficiency may cause growth problems and short stature. Most adults who have GH deficiency don't have any symptoms, but for some adults it can cause:

• Fatigue
• Muscle weakness
• Changes in body fat composition
• Lack of ambition
• Social isolation

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) deficiency

Deficiency of these hormones, called gonadotropins, affect the reproductive system. In women, the deficiency decreases egg and estrogen production from the ovaries. In men, the deficiency decreases sperm and testosterone production from the testicles. Women and men may experience a lower sex drive, infertility or fatigue. In children and adolescents, delayed puberty is usually the only symptom.

Women may also have symptoms such as:

• Hot flashes
• Irregular or no periods
• Loss of pubic hair
• An inability to produce milk for breast-feeding

Men may also have symptoms such as:

• Erectile dysfunction
• Decreased facial or body hair
• Mood changes

Thyroid-stimulating hormone (TSH) deficiency

This hormone controls the thyroid gland. A TSH deficiency leads to low levels of thyroid hormones (hypothyroidism). This causes symptoms such as:

• Fatigue
• Weight gain
• Dry skin
• Constipation
• Sensitivity to cold or difficulty staying warm

Adrenocorticotropic hormone (ACTH) deficiency

This hormone helps your adrenal glands work properly, and helps your body react to stress. Symptoms of ACTH deficiency include:

• Severe fatigue
• Low blood pressure, which may lead to fainting
• Frequent and prolonged infections
• Nausea, vomiting or abdominal pain
• Confusion

Anti-diuretic hormone (ADH) deficiency

This hormone, which is also called vasopressin, helps your body balance its fluid levels. An ADH deficiency can cause a disorder called diabetes insipidus, which can cause:

• Excessive urination
• Extreme thirst
• Electrolyte imbalances

Prolactin deficiency

Prolactin is the hormone that tells the body when to start making breast milk. Low levels of prolactin can cause women to have problems making milk for breast-feeding.

Hypopituitarism has a number of causes. In many cases, hypopituitarism is caused by a tumor of the pituitary gland. As a pituitary tumor increases in size, it can compress and damage pituitary tissue, interfering with hormone production. A tumor can also compress the optic nerves, causing visual disturbances.

In addition to tumors, certain diseases or events that cause damage to the pituitary gland may also trigger hypopituitarism. Examples include:

• Head injuries
• Brain surgery
• Radiation treatment to the head or neck
• Lack of blood flow to the brain or pituitary gland (stroke) or bleeding (hemorrhage) into the brain or pituitary gland
• Certain medications, such as narcotics, high-dose corticosteroids or certain cancer drugs called checkpoint inhibitors
• Inflammation of the pituitary gland caused by an abnormal immune system response (hypophysitis)
• Infections of the brain, such as meningitis, or infections that can spread to the brain, such as tuberculosis or syphilis
• Infiltrative diseases, which affect multiple parts of the body, including sarcoidosis, an inflammatory disease occurring in various organs; Langerhans cell histiocytosis, in which abnormal cells cause scarring in numerous parts of the body; and hemochromatosis, which causes excess iron deposits in the liver and other tissues
• Severe loss of blood during childbirth, which may cause damage to the front part of the pituitary gland (Sheehan's syndrome or postpartum pituitary necrosis)

In some cases, hypopituitarism is caused by a genetic mutation (inherited). These mutations affect the pituitary gland's ability to produce one or more of its hormones, often starting at birth or in early childhood.

Tumors or diseases of the hypothalamus, a portion of the brain situated just above the pituitary, also can cause hypopituitarism. The hypothalamus produces hormones of its own that directly affect the activity of the pituitary gland.

In some cases, the cause of hypopituitarism is unknown.