TABLE 4.

Tests Used to Diagnose Genetic/Hormonal Disorders in Obese Children

Test	Expected Result in Hormonal/ Genetic Disorder	Expected Result in Exogenous Obesity
T4, T3, TSH	Primary hypothyroidism: decreased fT4, normal or decreased T3, increased TSH Central hypothyroidism: decreased fT4, normal or decreased T3, normal or decreased TSH	Normal or mildly increased TSH, normal fT4, increased T3
IGF-1, IGFBP-3	Decreased in GHD	Usually in the normal range
ACTH, cortisol 24-h urine-free cortisol Salivary cortisol Diurnal cortisol rhythm Dexamethasone suppression	Cushing’s syndrome Variably high cortisol, variable ACTH Increased Increased Abnormal Abnormal	All usually in the normal range
Free testosterone	High in PCOS	Normal or mildly increased
Prolactin	High in prolactinoma, hypothalamic obesity, septo-optic dysplasia, antipsychotic medications, ROHHAD	Normal or low
Polysomnography	Central hypoventilation in ROHHAD	Normal or obstructive sleep apnea
Leptin	Very low/absent in leptin deficiency, high in leptin receptor mutation	High for age, but appropriate for BMI
MC4R sequencing	MC4R mutation	Normal
Methylation analysis	Prader-Willi syndrome	Normal
Parathyroid hormone	Very high in Albright’s hereditary osteodystrophy with pseudohypoparathyroidism	Normal if vitamin D sufficient
Chromosomal microarray	16p, 1q deletions	Normal

ACTH = adrenocorticotropic hormone; BMI = body mass index; GHD = growth hormone deficiency; IGF-1 = insulin-like growth factor-1; IGFBP-3 = insulin-like growth factor-binding protein-3; MC4R = melanocortin 4 receptor; PCOS = polycystic ovary syndrome; ROHHAD = rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation; TSH = thyroid-stimulating hormone.