Hypopituitarism

• Hypopituitarism refers to the inadequate production of one or more anterior pituitary hormones as a result of damage to the pituitary gland and/or hypothalamus.
• The majority of cases affect the anterior pituitary lobe (adenohypophysis), which accounts for 80% of the gland. The hormones produced from this lobe are growth hormone, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone (TSH), adrenocorticotropic hormone, and prolactin.
• When the posterior lobe (neurohypophysis) is also damaged, loss of antidiuretic hormone and oxytocin occurs.
• The most common cause of hypopituitarism is compression of the pituitary gland by a nonsecretory pituitary macroadenoma.

• Acquired
  • Tumors
    • Pituitary macroadenomas (≥ 10 mm in diameter) are the most common cause of hypopituitarism.
    • Less common: meningiomas, craniopharyngiomas, internal carotid artery aneurysms , Rathke cleft cyst (a benign, intrasellar/suprasellar cyst that arises from the remnants of the Rathke pouch ))
  • Pituitary apoplexy (Infarction of the pituitary gland as a result of ischemia and/or hemorrhage)
  • Sheehan syndrome: postpartum necrosis of the pituitary gland. Usually occurs following postpartum hemorrhage
  • Traumatic brain injury (especially around the skull base)
• Congenital
  • Hemochromatosis
  • Sarcoidosis
  • Infections: meningitis, TB, tertiary syphilis, toxoplasmosis, fungi (e.g., histoplasmosis)
  • Lymphocytic histiocytosis
  • Empty sella syndrome
  • Congenital deficiency of hypothalamic hormones
  • Iatrogenic

Symptoms are variable and depend on the specific hormone deficiency

• GH deficiency:
  • During childhood: short stature
  • During adulthood
    • Usually asymptomatic
    • Weight gain, weakness, and depression.
• Prolactin deficiency
  • Women: lactation failure following delivery
  • Men: asymptomatic
• FSH/LH deficiency
  • (LH and FSH) are the first affected hormones أول هرمونات تختفي
  • Women: primary amenorrhea (delayed puberty), secondary amenorrhea, irregular menstrual cycles, infertility
  • Men: delayed puberty, loss of libido, infertility, testicular atrophy, loss of facial, axillary and/or pubic hair, gynecomastia
• TSH deficiency: weight gain, cold intolerance, lethargy, constipation, dry skin (see “Hypothyroidism”)
• ACTH deficiency: weight loss, weakness, hypotension, chronic hyponatremia, hypoglycemia (see “Adrenal insufficiency”)
• ADH deficiency: Central diabetes insipidus à polyuria, polydipsia

• The first step in diagnosing pituitary insufficiency is to measure GH, TSH, LH, and IGF-1.
  • Growth hormone deficiency is tested by GH stimulation test (IGF-1 level is used as a screening test while GH stimulation test is confirmatory)
• To diagnose gonadotropin deficiency in women, measure LH, FSH, and estrogen. In males, gonadotropin deficiency can be detected by measuring LH, FSH, and testosterone.
• To diagnose TSH deficiency, measure serum thyroxine (T4) and free triiodothyronine (T3), which are low, with a normal to low TSH.

• Management of hypopituitarism involves treating the underlying causes. Multiple hormones must be replaced, but the most important is cortisol replacement.