Craniopharyngioma laboratory tests
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Marjan Khan M.B.B.S.[2]
Overview
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.
Laboratory Findings
The following hormones should be checked in patients who are being suspected of having craniopharyngioma.[1][2]
Metyrapone test
- 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 stimulation test
- 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-induced hypoglycemia test
- 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]
Serum insulin-like growth factor-1 (IGF-1)
- 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]
Provocative tests of growth hormone secretion
- 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]
References
- ↑ 1.0 1.1 1.2 Petito CK, DeGirolami U, Earle KM (April 1976). "Craniopharyngiomas: a clinical and pathological review". Cancer. 37 (4): 1944–52. PMID 1260697.
- ↑ 2.0 2.1 2.2 Rush JA, Younge BR, Campbell RJ, MacCarty CS (November 1982). "Optic glioma. Long-term follow-up of 85 histopathologically verified cases". Ophthalmology. 89 (11): 1213–9. PMID 6818504.
- ↑ Garrè ML, Cama A (August 2007). "Craniopharyngioma: modern concepts in pathogenesis and treatment". Curr. Opin. Pediatr. 19 (4): 471–9. doi:10.1097/MOP.0b013e3282495a22. PMID 17630614.
- ↑ Rx of Craniopharyngioma. Cancer gov. http://www.cancer.gov/types/brain/hp/child-cranio-treatment-pdq#link/_40_toc
- ↑ Rx of Craniopharyngioma. Cancer gov. http://www.cancer.gov/types/brain/hp/child-cranio-treatment-pdq#link/_40_toc
- ↑ Weiner HL, Wisoff JH, Rosenberg ME, Kupersmith MJ, Cohen H, Zagzag D, Shiminski-Maher T, Flamm ES, Epstein FJ, Miller DC (December 1994). "Craniopharyngiomas: a clinicopathological analysis of factors predictive of recurrence and functional outcome". Neurosurgery. 35 (6): 1001–10, discussion 1010–1. PMID 7885544.
- ↑ 7.0 7.1 Bunin GR, Surawicz TS, Witman PA, Preston-Martin S, Davis F, Bruner JM (October 1998). "The descriptive epidemiology of craniopharyngioma". J. Neurosurg. 89 (4): 547–51. doi:10.3171/jns.1998.89.4.0547. PMID 9761047.