Craniopharyngioma laboratory tests

Patients with craniopharyngioma may have abnormal pituitary hormone levels, which is suggestive of disruption of hormone production due to pressure effects on the pituitary gland. The hypothalamic-pituitary axis hormones, namely growth hormone, thyroid hormone, luteinising and follicle stimulating hormone should be measured together with cortisol levels and an assessment of serum and urine osmolality. In addition, an estimate of bone age and, for young females, ovarian ultrasonography is useful. Ideally, any abnormalities should be corrected pre-operatively but, at the very least, low cortisol levels and diabetes insipidus should be treated prior to a surgical procedure.

The following hormones should be checked in patients who are being suspected of having craniopharyngioma.^[1][2]

• • Serum Growth hormone
  • Serum Leutinizing hormone
  • Serum Follicle stimulating hormone
  • Serum Prolactin
  • Serum Thyroid stimulating hormone
  • Serum ACTH
  • Morning serum cortisol

• Metyrapone blocks 11-beta-hydroxylase , the enzyme that catalyzes the conversion of 11-deoxycortisol to cortisol, resulting in a reduction in cortisol secretion.^[3]
• Fall in serum cortisol is observed if the hypothalamic-pituitary-adrenal axis is normal.
• Increase in ACTH secretion and therefore an increase in adrenal steroidogenesis up to and including 11-deoxycortisol.^[4]

• Cosyntropin (ACTH) stimulates adrenal glands when they have not been stimulated for a prolonged period.^[1]
• The test is usually performed by administering 0.25 mg (25 units) of cosyntropin (synthetic ACTH) intramuscularly or intravenously.
• Serum cortisol 60 minutes later after administration of cosyntropin. ^[5]
• A serum cortisol concentration of ≥18 mcg/dL (497 nmol/L) is considered a normal response.^[1]

• Insulin administration is a sufficient stress to stimulate ACTH and therefore cortisol secretion.
• The test is performed by administering 0.1 unit of insulin per kg of body weight and measuring serum glucose and cortisol before and 15, 30, 60, 90, and 120 minutes after the injection. ^[2]
• In normal subjects serum cortisol increases to ≥18 mcg/dL (498 nmol/L) if the serum glucose falls to <50 mg/dL (2.8 mmol/L).^[6]

• A serum IGF-1 concentration lower than the age-specific lower limit of normal in a patient who has organic pituitary disease confirms the diagnosis of growth hormone deficiency.^[2]

• Insulin-induced hypoglycemia or the combination of arginine and growth hormone-releasing hormone (GHRH) is a potent stimulus of growth hormone release. ^[7]
• Subnormal increases in the serum growth hormone concentration in a patient who has organic pituitary disease confirms the diagnosis of growth hormone deficiency.^[7]

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