Table 1.

Diagnostic Algorithm for Pituitary Dysfunction

Pituitary Axis	First Test	Confirmatory Test
GH deficiency	Glucagon stimulation test: peak GH < 5μg/l	GHRH–arginine test: GH < cutoff based on age and BMI;22 OR ITT: peak GH < 3μg/l
ACTH deficiency	Glucagon stimulation test: peak cortisol < 350nmol/l (<12.7μg/dl)21	Metyrapone test: 11-DOC < 200nmol/l (<6.9μg/dl) OR if unavailable ACTH < 60ng/l despite cortisol < 200nmol/l (<7.2μg/dl); OR ITT: peak cortisol < 450nmol/l (<16.3μg/dl); supported by am cortisol < 100nmol/l (<3.62μg/dl)
Hyperprolactinemia	Prolactin > 375 mU/l (NR = 75–375)	Repeat prolactin > 375mU/l AND negative macroprolactin AND normal MRI pituitary with contrast
Gonadotrophin deficiency	Random testosterone < 10nmol/l (<2.9ng/ml) OR if SHBG low (<15nmol/l) FAI < 30; AND nonelevated LH (NR = 1.7–12.0 IU/l) and FSH (NR = 1.7–8.0 IU/l)	Repeat abnormal basal levels using morning (9–10 am) sample
TSH deficiency	Free T4 < 9.0pmol/l (<0.70ng/dl) OR free T3 < 2.5pmol/l (<0.16ng/dl); AND nonelevated TSH (NR = 0.30–4.22mU/l)	Repeat abnormal basal levels
ADH (vasopressin) deficiency (diabetes insipidus)	Symptoms of polyuria or polydipsia AND random urine osmolarity <750 mosmol/kg	Water deprivation test

11-DOC = 11-deoxycorticosterone; ACTH = adrenocorticotropic hormone; ADH = antidiuretic hormone; BMI = body mass index; FAI = free androgen index (100 × testosterone/SHBG); FSH = follicle-stimulating hormone; GH = growth hormone; GHRH = growth hormone-releasing hormone; ITT = insulin tolerance test; LH = luteinizing hormone; MRI = magnetic resonance imaging; NR = normal range; SHBG = sex hormone-binding globulin; TSH = thyroid-stimulating hormone.