Lab

• Documentation of >1 deficiencies of pituitary hormones: Hormones are tested individually.
• Deficiencies may be single or multiple
• Laboratory measurement of basal and stimulated hormone levels, and levels of their target hormones.
• Corticotropin:
  • Basal ACTH at 8–9 AM, low level is positive test
  • Metapyrone test: Induced reduction in serum cortisol should cause increase in ACTH secretion.
  • Corticotropin stimulation test: Administration of synthetic ACTH should stimulate adrenal cortisol production, unless adrenal atrophy is present.
• Thyrotropin:
  • Secondary hypothyroidism, rare in absence of other pituitary hormone deficiencies
  • Low free T4 with inappropriately normal or low TSH suggests TSH deficiency
  • TSH not a reliable screening test
  • Thyroid-releasing hormone (TRH) stimulation: Blunted response in secondary hypothyroidism
• Gonadotropins:
  • Men: Serum testosterone is surrogate for LH deficiency in patients with known hypothalamic or pituitary disease. LH is elevated in primary hypogonadism, and normal or low in secondary hypogonadism.
  • Women: In women with known pituitary disease, LH and FSH testing not necessary in the presence of normal menses.
  • In the presence of oligomenorrhea or amenorrhea, measure FSH and LH levels.
  • Serum estradiol is low in hypogonadotropic hypogonadism.
  • Vaginal cytology for estrogenization index
  • Exclude hyperprolactinemia
• Prolactin:
  • Isolated hypoprolactinemia is rare.
  • Prolactin deficiency prevents lactation.
  • In prolactin deficiency, basal plasma levels are low, and fail to rise after injection of TRH.
  • Elevated prolactin may accompany hypopituitarism due to the disruption of hypothalamic inhibitory influences.
• Growth hormone:
  • Growth hormone deficiency highly likely if >2 other pituitary hormones deficient.
  • Low serum IGF-1.
  • Provocative tests include insulin-induced hypoglycemia, and arginine plus arginine-growth hormone-releasing hormone. Positive tests show deficient serum growth hormone response.
• Genetic testing if indicated

• MRI of hypothalamic-pituitary region
• Radiographs: Chest, skull, hands, wrists (for bone age)
• Gonadotropin deficiency may result in osteoporosis

• Destruction of anterior pituitary
• Atrophy of adrenal cortex, thyroid, gonads