Advanced, Organ-Based and Clinical Sciences
Panhypopituitarism may be suspected, and diagnostic testing pursued as a result, when either a suspicious lesion or symptom presents in a patient. For example, if a patient is found to have a sellar mass, pituitary testing may be initiated even if the patient is otherwise asymptomatic given the known potential effect such lesions can have on pituitary function.
Panhypopituitarism is the deficient secretion of multiple pituitary hormones. As such, diagnostic testing is predicated on the demonstration of multiple deficiencies by conducting a panel of hormone evaluations.
ACTH (Adrenocorticotropic hormone)
ACTH levels are tested by obtaining measures of both cortisol and ACTH. To test cortisol levels, an 8 am serum cortisol level is collected. If the level is ≤3 mcg/dL (83 nmol/L, normal range 5 to 25 mcg/dL) on more than one occasion, cortisol deficiency can be diagnosed. If the ACTH level is also low, this suggests hypopituitarism. If the cortisol level is indeterminate, there are a few additional tests that can be performed to further clarify the diagnosis. These include the Metyrapone test, the Cosyntropin stimulation test, and the Insulin-induced hypoglycemia test.
Gonadotropins (Luteinizing Hormone/Follicle-Stimulating Hormone)
Male patients: LH levels in a male patient are tested by determining serum testosterone concentration and LH concentration. If both testosterone and LH are low, hypopituitarism is more likely
Female patients: In female patients, LH/FSH levels are obtained with serum estradiol levels and response to a medroxyprogesterone challenge is determined. If the serum hormone levels are low and the patient does not demonstrate menstrual bleeding with a 10-day course of medroxyprogesterone, hypopituitarism is likely.
TSH (Thyroid Stimulating Hormone)
TSH levels can be somewhat equivocal in hypopituitarism as they may not always be significantly reduced. As such, TSH levels are measured in combination with T4 and T3, with deficiencies in all three suggesting hypopituitarism.
Current lab testing typically results in equivocal findings regarding appropriate prolactin levels given the typically low circulating level in a non-pregnant/non-postpartum female and there is no current lab test for prolactin reserve. As such, clinical suggestion of low prolactin (as seen in postpartum women with inability to nurse and low serum levels) is the current standard for deficiency.
Deficiency can be determined three ways:
-The lack of appropriate serum GH response to other hormone stimulation testing (other hormone stimulation challenges should prompt an increase in GH)
-The deficiency of Insulin-Like Growth Factor
-The inadequate response to GH release with administration of GHRH and arginine (a <4.1 ng/mL increase in GH). However, GH is no longer available in the US so surrogate stimuli (arginine alone, clonidine, L-DOPA) are considered although they are more likely to result in false positives.