What are the causes and diagnostic tests for hyperhidrosis?

Causes and Diagnostic Evaluation of Hyperhidrosis

Hyperhidrosis is categorized as either primary (focal, bilateral, symmetric sweating without underlying cause) or secondary (generalized or focal sweating due to medications or systemic conditions), and the diagnostic workup must first exclude secondary causes through targeted history, physical examination, and selective laboratory testing before diagnosing primary hyperhidrosis. 1, 2

Classification and Etiology

Primary Hyperhidrosis

• Affects approximately 2.8-4.8% of the US population and typically presents with bilateral, symmetric, focal excessive sweating 1, 3, 2
• Most commonly affects the axillae, palms, soles, and craniofacial regions 1, 3
• Onset typically occurs in childhood or adolescence 4
• Results from autonomic nervous system dysfunction causing neurogenic overactivity of otherwise normal eccrine sweat glands, or aberrant central control of emotions 2
• Approximately 93% of hyperhidrosis patients have primary disease 2

Secondary Hyperhidrosis

• Presents with generalized or asymmetric distribution and is caused by underlying medical conditions or medications 1, 3, 2
• Key underlying conditions to consider:
  • Endocrine disorders: Hyperthyroidism (warm/moist skin, heat intolerance, tremor, low TSH), hypothyroidism, diabetes mellitus, hypercalcemia/hyperparathyroidism, acromegaly 5, 6
  • Neurologic conditions: Parkinson disease 6
  • Medications: Drug-induced hyperhidrosis 6, 4
  • Infectious diseases: Various systemic infections 5
  • Malignancy: Including lymphoma 5
  • Cardiovascular disease: Heart failure can present with diaphoresis 5

Diagnostic Approach

History and Physical Examination

The initial evaluation must focus on distinguishing primary from secondary hyperhidrosis through specific clinical features:

• Distribution pattern: Focal and bilateral suggests primary; generalized or asymmetric suggests secondary 1, 3, 2
• Age of onset: Childhood/adolescence favors primary hyperhidrosis 4, 2
• Medication review: Comprehensive list of current and recent medications 6, 4
• Review of systems targeting secondary causes:
  • Thyroid symptoms: Heat/cold intolerance, weight changes, tremor, skin changes 5
  • Diabetes symptoms: Polyuria, polydipsia, weight loss 5
  • Neurologic symptoms: Tremor, rigidity, gait changes 6
  • Cardiac symptoms: Dyspnea, orthopnea, edema 5
  • Constitutional symptoms: Fever, night sweats, weight loss 5

Laboratory Testing

When secondary hyperhidrosis is suspected based on clinical features, targeted laboratory evaluation should include:

• Thyroid function tests (TSH, free T4): Essential screening test as both hyperthyroidism and hypothyroidism can cause or contribute to hyperhidrosis 5
• Fasting glucose or hemoglobin A1c: Screen for diabetes mellitus, particularly in patients with risk factors 5
• Complete blood count: Evaluate for infection or hematologic abnormalities 5
• Serum calcium and parathyroid hormone: If hypercalcemia suspected 5
• Additional tests based on clinical suspicion:
  • Serum electrolytes (including magnesium) 5
  • Renal and hepatic function tests 5
  • HIV screening in high-risk patients 5

Severity Assessment

• Use the Hyperhidrosis Disease Severity Scale to grade tolerability and impact on quality of life, which guides treatment decisions 1

Clinical Pitfalls

Common diagnostic errors to avoid:

• Never diagnose primary hyperhidrosis without first excluding secondary causes through appropriate history, examination, and selective laboratory testing 1, 3, 2
• Generalized or asymmetric sweating patterns should always prompt investigation for secondary causes 3, 2
• Adult-onset hyperhidrosis warrants more aggressive evaluation for secondary causes compared to childhood-onset disease 4, 2
• The presence of constitutional symptoms (fever, weight loss, night sweats) mandates thorough evaluation for underlying systemic disease 5