What specific hormone tests are recommended for patients with obesity seeking weight loss?

Specific Hormone Testing for Patients with Obesity Seeking Weight Loss

For patients with obesity seeking weight loss, a basic laboratory evaluation should include comprehensive metabolic panel, fasting lipid profile, thyroid function tests, and screening for abnormal blood glucose, with additional targeted hormone testing based on clinical presentation. 1

Core Laboratory Tests for All Patients with Obesity

• Basic Laboratory Panel:

  • Comprehensive metabolic panel (liver and kidney function)
  • Fasting lipid profile (total cholesterol, HDL, LDL, triglycerides)
  • Thyroid function tests (TSH, free T4)
  • Fasting blood glucose and HbA1c 1

• Anthropometric Measurements:

  • BMI calculation
  • Waist circumference measurement (≥102 cm for men and ≥88 cm for women indicates increased cardiometabolic risk) 1

Hormone Testing Based on Clinical Presentation

For All Patients:

• Thyroid Function Tests:
  • TSH and free T4 (recommended for all patients with obesity regardless of symptoms) 2, 3

For Men with Symptoms of Hypogonadism:

• Sex Hormone Panel:
  • Morning total testosterone (essential)
  • Sex hormone-binding globulin (SHBG)
  • Free testosterone calculation or direct measurement
  • Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) 4

For Women with Irregular Menstruation or Hirsutism:

• PCOS Evaluation:
  • Total testosterone
  • Free androgen index (total testosterone/SHBG ratio)
  • SHBG
  • Androstenedione
  • DHEAS (dehydroepiandrosterone sulfate) 1, 4

For Suspected Cushing's Syndrome:

• Cortisol Testing:
  • 1-mg overnight dexamethasone suppression test
  • 24-hour urinary free cortisol
  • Late-night salivary cortisol 1, 5

Additional Testing Based on Specific Findings

• If Acanthosis Nigricans Present:

  • Fasting insulin levels
  • HOMA-IR (homeostasis model assessment of insulin resistance) 1

• If Sleep Disturbances Present:

  • Screen for obstructive sleep apnea using validated tools (Epworth Sleepiness Scale, STOPBANG questionnaire) 1

• If Osteoporosis Suspected:

  • Vitamin D levels
  • Parathyroid hormone levels 6

Interpretation and Clinical Significance

• Thyroid Function: Hypothyroidism is common in obesity and should be treated if present, though weight loss effects from treatment are modest 2, 3

• Sex Hormones:

  • In men: Low total testosterone with normal/low SHBG suggests obesity-related hypogonadism
  • In women: Elevated free androgen index (>0.3) suggests PCOS 4

• Cortisol: Elevated cortisol with failure to suppress after dexamethasone suggests Cushing's syndrome, though this is rare in obesity (<0.6% prevalence) 5

Clinical Pitfalls to Avoid

1. Over-testing: Most endocrine testing is not recommended in the absence of specific clinical features suggesting an endocrine disorder 3

2. Misinterpreting Results: Many hormonal abnormalities in obesity are consequences rather than causes of obesity and normalize with weight loss 6, 5

3. Overlooking Secondary Causes: While rare, endocrine disorders like Cushing's syndrome, hypothyroidism, and insulinoma can cause or exacerbate obesity and should be ruled out when clinically suspected 7

4. Ignoring SHBG: Low SHBG is common in obesity and affects interpretation of total testosterone levels; free testosterone or bioavailable testosterone should be measured in obese patients 4

5. Missing PCOS: In women with obesity, PCOS is common and may benefit from specific treatments including anti-obesity medications like exenatide or liraglutide 1, 4

Remember that successful weight loss often normalizes many hormone abnormalities found in obesity, including TSH elevation and testosterone levels, suggesting these are often consequences rather than causes of obesity 5.