Hypopituitarism

What the pituitary gland does

The pituitary sits in a bony pocket under the brain, just below the optic nerves. Its front part (anterior pituitary) makes six hormones and its back part (posterior pituitary) releases two:

Hormones are usually lost in a typical order, often growth hormone and LH/FSH first, and ACTH and TSH later. Panhypopituitarism means all or most hormones are deficient.

Causes

Pituitary tumors

Pituitary adenomas, almost always benign, are the most common cause. They compress normal pituitary tissue. Large tumors can also press on the optic nerves, causing loss of side vision.

Treatment of pituitary or brain tumors

• Pituitary surgery
• Radiation therapy to the brain or pituitary, which may cause deficiencies years later

Other causes

• Traumatic brain injury and subarachnoid hemorrhage
• Pituitary apoplexy: sudden bleeding into a pituitary tumor
• Sheehan syndrome: pituitary damage from severe blood loss during childbirth
• Other tumors: craniopharyngioma, meningioma, metastases
• Inflammatory and infiltrative diseases: hypophysitis (including from cancer immunotherapy), sarcoidosis, hemochromatosis, Langerhans cell histiocytosis
• Infections such as tuberculosis or meningitis
• Genetic conditions affecting pituitary development
• Medicines: long-term high-dose steroids or opioids can suppress pituitary signals

Symptoms

Symptoms develop gradually in most cases and depend on which hormones are missing (see the table above). Common combinations include:

• tiredness, weakness and low energy
• feeling cold
• weight gain or weight loss
• low libido, erectile dysfunction, irregular or absent periods and infertility
• pale skin and loss of body hair
• low mood and poor concentration
• dizziness on standing
• headaches and vision changes with large tumors

In acute cases such as pituitary apoplexy, symptoms come on suddenly with severe headache and collapse.

Diagnosis

1. Blood tests of both pituitary hormones and their target hormones, ideally in the morning: - cortisol and ACTH - TSH and free T4 (in hypopituitarism, both are low, unlike primary hypothyroidism where TSH is high) - LH, FSH, testosterone or estradiol - IGF-1 for growth hormone - prolactin - sodium and urine concentration for diabetes insipidus
2. Stimulation tests: such as the ACTH (Synacthen) test or growth hormone stimulation tests.
3. MRI of the pituitary to look for a tumor or other cause.
4. Visual field testing if a tumor is near the optic nerves.

Treatment

Hormone replacement

• Cortisol: hydrocortisone tablets, usually started before thyroid hormone if both are needed, because thyroid hormone alone can trigger an adrenal crisis.
• Thyroid hormone: levothyroxine, adjusted using free T4 levels (TSH is not useful for monitoring in hypopituitarism).
• Sex hormones: testosterone for men, estrogen with progestogen for women before natural menopause age. Fertility treatment with gonadotropin injections is possible.
• Growth hormone: daily or weekly injections in children and selected adults.
• Desmopressin for diabetes insipidus.

Treating the cause

• Surgery, usually through the nose (transsphenoidal), for many pituitary tumors
• Medicines for prolactinomas (dopamine agonists), which shrink the tumor and lower high prolactin
• Radiation for residual or recurrent tumors
• Steroids for some inflammatory causes

Sick day rules and emergency care

People taking hydrocortisone need to:

• double or triple their dose during fever or significant illness, as advised by their endocrinologist
• use an emergency hydrocortisone injection if vomiting or unable to take tablets, and seek urgent help
• wear a medical alert bracelet and carry a steroid emergency card
• increase steroid cover for surgery, labor and major procedures

Outlook

With proper hormone replacement and monitoring, most people with hypopituitarism lead normal, active lives. Regular follow-up with an endocrinologist adjusts doses and watches for new deficiencies. Untreated cortisol deficiency is the main danger, so education about adrenal crisis is essential.

Frequently asked questions

What is hypopituitarism?

Hypopituitarism is a condition in which the pituitary gland does not make enough of one or more of its hormones. Because these hormones control the thyroid, adrenal glands, sex organs, growth and water balance, it can affect many body functions.

What are the symptoms of hypopituitarism?

Symptoms depend on which hormones are missing and can include tiredness, weakness, feeling cold, weight changes, low sex drive, erectile dysfunction, missed periods, infertility, loss of body hair, dizziness and, with ADH deficiency, extreme thirst and urination.

What causes hypopituitarism?

The most common cause is a pituitary tumor or its treatment with surgery or radiation. Other causes include head injury, bleeding into the pituitary, severe blood loss in childbirth (Sheehan syndrome), inflammation, infections and genetic conditions.

Is hypopituitarism life-threatening?

It can be if cortisol deficiency is untreated, because illness or stress can trigger an adrenal crisis with collapse and low blood pressure. With hormone replacement and sick day rules, people with hypopituitarism can live normal lives.

Can hypopituitarism be reversed?

Sometimes. Removing or shrinking a tumor that is compressing the gland, or treating inflammation, can restore some function. In many people, however, the damage is permanent and lifelong hormone replacement is needed.