Hypopituitarism

Clinic

• Decreased secretion of one or more of 8 hormones normally produced by the pituitary gland at the base of the brain.
• If there is decreased secretion of one specific pituitary hormone, the condition is known as selective hypopituitarism.
• Panhypopituitarism: If there is decreased secretion of most or all hormones

Signs / Symptoms

• The most common problem is insufficiency of FSH and/or LH leading to sex abnormalities.
• Growth hormone deficiency is more common in people with an underlying tumor than those with other causes.

Autoimmune hypophysitis

• It can lead to deficiencies in one or more pituitary hormones, causing
  • Central diabetes insipidus
  • Central adrenal insufficiency
  • Central hypothyroidism

• Therefore Autoimmune hypophysitis could be considered as secondary Hypogonadism / Hypothyroidism / Adrenal insufficiency

Types

LAH can thus be classified as:

1. Lymphocytic adenohypophysitis
2. Posterior pituitary: LINH (Lymphocytic infundibular neurohypophysitis)
3. Both LAH and LINH may also lead to symptoms of an intracranial mass such as headache or disturbance of vision

1- LAH: Lymphocytic adenohypophysitis

• It is characterized by infiltration of the pituitary stalk with lymphocytes, as the name would suggest. Importantly, there is a paucity of plasma cells or granulomas, differentiating it from IgG4-related hypophysitis and granulomatous hypophysitis (e.g. due to neurosarcoidosis) respectively.
• Most common
• It mimics a pituitary adenoma
• It is closely related to other inflammatory conditions in the region, namely orbital pseudotumor and Tolosa-Hunt syndrome.
• It has endocrine hormone deficits (Hypopituitarism)
• TSH producing cell deficit results in secondary Hypothyroidism
• ACTH producing cell Adrenal insufficiency
• LH and/or FSH producing cells deficit results in secondary Hypogonadism
• Interruption of dopamine flow from hypothalamus into pituitary, causing high levels of Prolactin
• Causation: MTB (Tuberculosis Hypophysitis)

Associations

Autoimmune conditions such as

• Autoimmune thyroiditis: HCV, MMP, EBV, MTB
• Pernicious anemia: EBV, HCV
• SLE
• Rheumatoid arthritis
• Dacryoadenitis : EBV, MMP, MTB
• ipilimumab: monoclonal antibody drugs

2- LINH : Lymphocytic Infundibuloneurohypophysitis

• Rare
• occurs when the posterior pituitary is affected resulting in diabetes insipidus.
• Common symptoms include nausea, vomiting, fatigue, loss of libido, amenorrhea, and dizziness.
• Mass effects on adjacent structures (e.g. optic chiasm)

3- Both anterior and posterior pituitary

Lymphocytic infundibular panhypophysitis

Antibodies

80% of patients with pituitary antibodies also have antibodies to thyroid gland or its hormones. Likewise, 20% of autoimmune thyroid patients also have pituitary antibodies. It follows that a subset of thyroid patients may have a disease related to autoimmune hypophysitis. Recent research has focused on a defect at the CTLA-4 gene which, coupled with other factors, may result in autoimmunity primarily focusing on certain endocrine glands including the pituitary and thyroid.