Test	Indication	Abnormal (reference range)*	Clinical notes
24-hour urine free cortisol	Cortisol excess	Elevated (10 to 84 mcg total per 24-hour period)	Urine collection must be accurate and total
			High false-positive rate in women taking estrogen
			Diagnostic if four times greater than normal
Adrenocorticotropic hormone	Determine source of excess cortisol	Elevated (6 to 48 pg per mL [1 to 11 pmol per L])	Levels will be elevated with pituitary or ectopic source of excess cortisol
Estradiol	Hormone deficiency in females	Low (1.5 to 3 pg per mL [6 to 11 pmol per L])†	Not accurate in women taking oral contraceptives or hormone therapy
			Values vary based on phase of menstrual cycle
Free T4	Thyroid deficiency	Low (4.2 to 13 ng per dL [54 to 167 pmol per L])	Low T4 with normal or low TSH indicates secondary hypothyroidism (possibly from pituitary dysfunction)
Late night salivary cortisol	Cortisol excess	Elevated (< 0.01 to 0.09 mcg per dL)	Midnight sample
Low-dose dexamethasone suppression	Initial test for cortisol excess	Elevated (serum cortisol ≥ 1.8 ng per dL)	1 mg of dexamethasone given at 11 p.m., cortisol test at 8 a.m.
			Abnormal if cortisol levels fail to decrease to < 1.8 ng per dL
			High false-positive rate in women taking estrogen
			Further testing needed to rule out the source of excess cortisol and to rule out “pseudo–Cushing syndrome”
Oral glucose suppression	Acromegaly (excess growth hormone) confirmatory test	Elevated (0 to 1 ng per mL)†	Failure of growth hormone to decrease to < 1 ng per mL two hours after administering 75 g of oral glucose
Serum alpha-subunit	Determine if nonfunctioning or gonadotroph-secreting tumor	Elevated (0.04 to 1.23 ng per mL)†	Test for the alpha subunit common to LH, FSH, TSH, and hCG
			May be overproduced in some pituitary adenomas (most commonly gonadotroph- and thyrotroph-secreting types)
			Useful if elevated LH/FSH levels and etiology of elevation is unknown
Serum cortisol	Cortisol deficiency	Low (8 to 19 mcg per dL [221 to 524 nmol per L])	Early morning testing
			If < 13 mcg per dL (359 nmol per L), patient should undergo dynamic testing
Serum insulinlike growth factor 1	Excess growth hormone	Elevated (76 to 328 ng per mL [10 to 43 nmol per L])‡	High sensitivity
			Normally elevated during pregnancy
			May be low in patients with poorly controlled diabetes mellitus, liver disease, hypothyroidism, and malnutrition
Serum LH/FSH	Gonadotroph-secreting tumor	Elevated	In postmenopausal women, elevated LH/FSH levels are normal
		FSH (2 to 35 mIU per mL [2 to 35 IU per L])†	Value for menstruating women varies based on phase of menstrual cycle
		LH (1.5 to 50 mIU per mL [1.5 to 50 IU per L])†
	Hypogonadism	Low
		FSH (2 to 35 mIU per mL)†
		LH (1.5 to 50 mIU per mL)†
Serum macroprolactin	Hyperprolactinemia	Present	Biologically inactive form of prolactin, with no pathologic association
			Useful to check in patients with hyperprolactinemia who have moderate elevations (100 to 300 mcg per L [4,348 to 13,043 pmol per L]) of serum prolactin with unknown etiology or when radiographic findings and clinical presentation are not consistent with serum prolactin level
Serum prolactin	Hyperprolactinemia	Elevated (3 to 24 mcg per L [130 to 1,043 pmol per L])	≥ 250 mcg per L (10,870 pmol per L) highly suggestive of prolactinoma
			Moderate elevations (25 to 249 mcg per L [1,087 to 10,826 pmol per L]) should prompt investigation of other causes of hyperprolactinemia
			Serum level correlates with tumor size; when level does not correlate with size, consider serial dilutions
Serum TSH	Evaluate thyrotroph-secreting tumor	Elevated (0.5 to 4.8 mIU per L)	May be atypically normal in relation to free T4
	Thyroid hormone deficiency	Low (0.5 to 4.8 mIU per L)
Testosterone (total)	Hormone deficiency in males	Low (350 to 1,030 ng per dL [12 to 36 nmol per L])‡	Total (free + protein-bound) alone is generally an accurate picture of testosterone level
Testosterone (free)		Low (52 to 280 pg per mL)‡	Measurements should be taken at 8 a.m.