Hypopituitarism

Summary

Hypopituitarism is a condition characterized by pituitary hormone deficiency. This condition primarily results from a disease of the pituitary gland , but it may arise from hypothalamic dysfunction. Pituitary tumors are one of the most common causes. 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. All of these hormones regulate the activities of different organs, and thus the effects of pituitary hypofunction are multisystemic. The diagnosis is made through a combination of clinical findings, hormone levels, provocation tests, and brain imaging. Treatment is hormone replacement and addressing the etiology.

Overview

• 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.

Causes

• 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

Clinical features

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

Diagnosis

• 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.

Treatment

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

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