What initial laboratory tests should be obtained in an obese adult to screen for common obesity‑related comorbidities?

Initial Laboratory Evaluation in Obese Adults

All adults with obesity require a comprehensive metabolic panel, fasting lipid profile (total cholesterol, LDL-C, HDL-C, triglycerides, non-HDL-C), thyroid-stimulating hormone (TSH), and either hemoglobin A1c or fasting glucose as the essential baseline laboratory workup. 1

Core Metabolic Panel

• The comprehensive metabolic panel screens for kidney dysfunction (creatinine, eGFR, BUN), liver disease (AST, ALT, alkaline phosphatase), and electrolyte abnormalities—all highly prevalent complications in obesity. 1
• Liver enzyme elevation warrants screening for non-alcoholic fatty liver disease (NAFLD), which affects a substantial proportion of obese patients and can progress to cirrhosis. 2

Glucose Metabolism Assessment

• Hemoglobin A1c ≥6.5% defines diabetes; 5.7–6.4% defines pre-diabetes. 1
• Alternatively, fasting plasma glucose ≥126 mg/dL confirms diabetes, while 100–125 mg/dL indicates pre-diabetes. 1
• Screen all obese adults aged 40–70 years for abnormal glucose as part of cardiovascular risk stratification. 1

Lipid Profile Requirements

• The fasting lipid panel must include total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, and calculated non-HDL-cholesterol to quantify dyslipidemia and estimate cardiovascular risk. 1
• This panel identifies the atherogenic dyslipidemia pattern (elevated triglycerides, low HDL-C, small dense LDL particles) characteristic of obesity-related metabolic syndrome. 2

Thyroid Function Screening

• Universal TSH measurement is mandatory because hypothyroidism is highly prevalent in obesity and represents a reversible contributor to weight gain. 1
• Do not omit thyroid testing even in the absence of classic hypothyroid symptoms, as obesity itself can mask these features. 1

Blood Pressure and Metabolic Syndrome Criteria

• Measure blood pressure with an appropriately sized cuff; hypertension is defined as ≥130/80 mmHg. 1
• Metabolic syndrome requires ≥3 of the following: waist circumference ≥88 cm (women) or ≥102 cm (men); triglycerides ≥150 mg/dL; fasting glucose ≥100 mg/dL; blood pressure ≥130/85 mmHg; HDL-C <40 mg/dL (men) or <50 mg/dL (women). 1

Anthropometric Measurements

• Calculate BMI and measure waist circumference at the midpoint between the last rib and iliac crest to quantify both total and abdominal adiposity. 2
• Standard waist circumference thresholds indicating increased metabolic risk are ≥102 cm (40 inches) for men and ≥88 cm (35 inches) for women. 2

Ethnicity-Specific Adjustments

• Apply lower BMI cut-points for South and Southeast Asian populations: ≥23 kg/m² defines overweight, as these groups develop metabolic complications at lower thresholds. 2, 1
• Use ethnicity-specific waist circumference thresholds: ≥90 cm for Asian men and ≥80 cm for Asian women. 2, 1

Medication Review

• Systematically review all current medications that promote weight gain, including psychiatric agents (antipsychotics, mood stabilizers), systemic corticosteroids, insulin, sulfonylureas, and certain beta-blockers. 1
• Optimize or substitute weight-promoting medications when clinically feasible. 1

Physical Examination Findings Requiring Additional Testing

• Acanthosis nigricans (hyperpigmented, velvety skin in body folds) signals insulin resistance and mandates glucose and metabolic assessment. 1
• Hirsutism (male-pattern hair growth in women) suggests polycystic ovary syndrome and warrants reproductive hormone evaluation. 1
• Increased neck circumference indicates obstructive sleep apnea risk and requires screening with validated questionnaires (STOP-BANG or Epworth Sleepiness Scale). 1
• Thin, fragile skin with easy bruising, wide purple striae (>1 cm), or proximal muscle weakness raises suspicion for Cushing's syndrome and necessitates endocrine workup. 1

Conditional Endocrine Testing (Only When Specific Features Present)

• Test for Cushing's syndrome only if thin atrophic skin, easy bruising, wide purple striae, proximal weakness, or rapid central weight gain with peripheral leanness are observed. 1
• Evaluate for polycystic ovary syndrome when hirsutism or acanthosis nigricans is present. 1
• Assess testosterone levels in men reporting decreased libido, erectile dysfunction, loss of muscle mass, or gynecomastia. 1
• Consider IGF-1 testing for growth hormone deficiency only in patients with pituitary disease history, cranial irradiation, or severe fatigue with muscle loss. 1

Hepatic Fibrosis Risk Stratification

• When liver enzymes are elevated, calculate the Fibrosis-4 (FIB-4) index to estimate hepatic fibrosis risk and guide further evaluation for NAFLD progression. 1
• All guidelines recommend excluding competing causes of liver disease, including viral hepatitis (hepatitis B and C serology), autoimmune hepatitis (autoimmune markers), hemochromatosis (iron studies), Wilson disease (ceruloplasmin, copper), and alpha-1 antitrypsin deficiency. 2

Common Pitfalls to Avoid

• Do not rely on BMI alone—incorporate waist circumference measurements and apply ethnicity-specific thresholds to avoid underestimating metabolic risk. 1
• Do not skip TSH testing based on absence of classic hypothyroid symptoms, as hypothyroidism is a common and treatable contributor to obesity. 1
• Do not order comprehensive endocrine panels routinely—reserve Cushing's, PCOS, and hypogonadism testing for patients with specific clinical features. 1
• Do not use standard BMI cut-points for Asian populations—apply lower thresholds (≥23 kg/m² for overweight) to capture increased metabolic risk. 2, 1