Which hormones should be evaluated in a patient with obesity?

Hormonal Evaluation in Obesity

In patients with obesity, routine thyroid function testing (TSH) is recommended for all patients, while screening for Cushing's syndrome should only be performed in those with unexplained weight gain combined with growth deceleration (in children) or specific clinical features suggestive of hypercortisolism (in adults). 1

Essential Hormone Testing

Thyroid Function - Universal Screening

• TSH should be checked in all patients with obesity given the high prevalence of hypothyroidism in this population 1
• This is the only hormone test recommended universally without specific clinical suspicion
• Thyroid hormone levels are typically normal in obesity except for T3, which may be elevated 2

Cushing's Syndrome - Selective Screening Only

Screen only when specific clinical features are present:

In Children and Adolescents:

• Screen ONLY if: Unexplained weight gain PLUS either decreased height velocity OR declining height standard deviation score 3
• This combination has high sensitivity and specificity for Cushing's syndrome
• Growth failure reliably distinguishes simple obesity from Cushing's syndrome in prepubertal children
• Post-pubertal adolescents require assessment according to adult guidelines 3

In Adults:

Screen when clinical features suggest hypercortisolism:

• Central obesity with thin, atrophic skin
• Purple striae (>1 cm wide)
• Proximal muscle weakness
• Easy bruising
• Facial plethora
• Unexplained osteoporosis 4

Diagnostic Tests for Cushing's Syndrome (when indicated):

1. 24-hour urinary free cortisol (UFC) - 2-3 collections
2. Late-night salivary cortisol (≥2 tests on consecutive days)
3. Overnight 1 mg dexamethasone suppression test
4. If confirmed, measure 9:00 AM plasma ACTH to distinguish ACTH-dependent from ACTH-independent causes 5

Sex Hormone Testing - Only With Clinical Suspicion

In Men:

Test only if symptoms suggest hypogonadism:

• Decreased energy, libido, muscle mass, body hair
• Hot flashes, gynecomastia, infertility 6

When testing:

• Morning (8-10 AM) total testosterone
• Free testosterone by equilibrium dialysis
• Sex hormone-binding globulin (SHBG)
• If low, repeat testing plus LH/FSH to distinguish primary from secondary hypogonadism 6

In Women:

Test only if clinical features suggest PCOS:

• Hirsutism, acne, androgenic alopecia
• Oligomenorrhea or amenorrhea
• Infertility 7

When testing:

• Total testosterone (preferably by LC-MS/MS)
• Free androgen index (FAI)
• Consider androstenedione, DHEAS 7

What NOT to Test Routinely

The following are NOT recommended without specific clinical suspicion:

• Growth hormone/IGF-1 (normal or elevated IGF-1 in obesity) 2
• Prolactin (normal in obesity, though response to stimuli may be blunted) 2
• Cortisol/ACTH in absence of Cushing's features 1
• Routine sex hormones without symptoms 1
• Vitamin D (though deficiency is common, not part of endocrine obesity workup) 8

Critical Clinical Pitfalls

Common mistakes to avoid:

• Do not perform extensive endocrine testing in simple obesity - most hormonal abnormalities are secondary to obesity itself and normalize with weight loss 1
• Do not screen for Cushing's in every obese patient - it is extremely rare, and false positives are common due to pseudo-Cushing's states (severe obesity, uncontrolled diabetes, PCOS, depression) 5
• In men, do not rely on total testosterone alone - measure free testosterone, as obesity lowers SHBG, which can make total testosterone appear low despite normal free testosterone 6
• Weight loss should be the primary intervention - treating mild hormonal abnormalities has only modest effects on weight, whereas weight loss corrects most endocrine dysfunction 1

Algorithm Summary

1. All patients: Check TSH
2. Children with obesity: Screen for Cushing's ONLY if weight gain + growth failure
3. Adults with obesity: Screen for Cushing's ONLY if specific cushingoid features present
4. Men with symptoms: Morning testosterone, free testosterone, SHBG
5. Women with symptoms: Testosterone, FAI for suspected PCOS
6. No other routine endocrine testing unless specific clinical syndrome suspected

The key principle: Obesity itself causes hormonal changes that normalize with weight loss. Focus on weight management rather than extensive hormonal workup unless specific endocrine syndromes are clinically suspected. 8, 1