What laboratory tests are recommended for evaluating a patient with symptoms of panic disorder?

Laboratory Testing for Panic Disorder Evaluation

Order TSH as the primary and essential laboratory test for all patients presenting with panic disorder symptoms, and add free T4 only if TSH is abnormal or clinical suspicion for thyroid disease is high. 1

Core Thyroid Screening

The relationship between thyroid dysfunction and panic disorder is bidirectional and clinically significant, making thyroid screening the cornerstone of laboratory evaluation:

• TSH (thyroid-stimulating hormone) is the single most important laboratory test for panic disorder evaluation and should be obtained routinely 1
• Free T4 should be added selectively when TSH is abnormal or when clinical features suggest thyroid disease 1
• The comorbidity between panic disorder and thyroid disorders is substantial: studies show 2-9% of panic disorder patients have thyroid disease, with higher rates in females 2
• Thyroid dysfunction can both mimic and exacerbate panic symptoms, as thyroid hormone receptors are present throughout the limbic system that regulates anxiety 3

Evidence Against Routine Extensive Testing

Do not order routine laboratory batteries beyond thyroid function testing unless specific clinical indicators are present:

• Extensive screening for conditions like pheochromocytoma, hypoglycemia, and Cushing's disease is not recommended as routine practice 4
• These rare conditions (pheochromocytoma, hypoglycemia) can present with panic-like symptoms, but routine screening is not cost-effective or evidence-based 4, 5
• The yield of detecting these conditions through routine screening in panic disorder patients is extremely low 4

Selective Additional Testing

Order additional laboratory tests only when guided by specific clinical findings:

• Medical history red flags: New onset in elderly patients, first-time psychiatric presentation, presence of vital sign abnormalities, or concurrent medical symptoms 1
• Physical examination findings: Tachycardia beyond what's expected during panic attacks, weight changes, heat/cold intolerance, tremor, or other signs suggesting medical illness 6
• Substance use screening: Consider when history suggests alcohol or drug abuse, as these commonly co-occur with panic disorder 1, 7
• Cardiac evaluation: Reserve for patients with chest pain and cardiac risk factors, not as routine screening 7

Clinical Context and Common Pitfalls

Avoid the trap of extensive medical workups that delay psychiatric treatment:

• Panic disorder patients often present with somatic symptoms (chest pain, dizziness, gastrointestinal distress) that can trigger expensive and potentially iatrogenic medical testing 7
• The most common misdiagnoses involve cardiac and neurologic conditions, leading to unnecessary emergency department visits and testing 5
• Medical causes should be considered but not exhaustively pursued without clinical indicators beyond the panic symptoms themselves 1

Practical Algorithm

For a patient presenting with suspected panic disorder:

1. Obtain TSH on all patients at initial evaluation 1
2. Add free T4 if TSH is abnormal (elevated or suppressed) 1
3. Perform targeted testing only based on history and physical examination findings suggesting specific medical conditions 1, 6
4. Screen for substance use disorders given high comorbidity 1
5. Do not routinely screen for pheochromocytoma, hypoglycemia, hyperparathyroidism, or other rare conditions unless clinical features specifically suggest these diagnoses 4

The evidence strongly supports a focused approach centered on thyroid screening, with additional testing reserved for patients with clinical indicators of underlying medical disease rather than routine extensive laboratory panels 1, 4.