Why is checking Thyroid-Stimulating Hormone (TSH) levels important in the evaluation of anxiety?

Why Check TSH for Anxiety

Checking TSH is essential when evaluating anxiety because there is significant comorbidity between anxiety disorders and thyroid dysfunction, with routine thyroid screening recommended as standard practice for all patients presenting with anxiety symptoms. 1, 2

Clinical Rationale for TSH Screening

Significant Comorbidity Between Conditions

• Nearly all studies demonstrate significant comorbidity between anxiety disorders and thyroid disorders, making thyroid screening a clinical imperative rather than optional 1
• Both subclinical hypothyroidism and subclinical hyperthyroidism significantly increase anxiety scores compared to euthyroid patients 3
• Among patients with abnormally elevated TSH, 83.5% had comorbid anxiety disorders 4

Symptom Overlap Creates Diagnostic Confusion

• Hyperthyroidism mimics core anxiety symptoms including nervousness, palpitations, shortness of breath, increased perspiration, fatigue, poor concentration, and disturbed sleep 1, 5
• These somatic symptoms overlap extensively with panic disorder presentations and generalized anxiety disorder criteria 1
• Without TSH screening, you risk treating primary thyroid disease as a psychiatric condition 1, 5

Bidirectional Relationship

Thyroid Dysfunction Can Cause Anxiety

• Thyroid hormone receptors are present throughout the limbic system, which directly regulates emotions including anxiety 5, 6
• The cross-communication between thyroid, noradrenergic, and serotonergic systems means thyroid deficiency disrupts multiple neurotransmitter pathways involved in anxiety regulation 5
• Untreated diagnosed hypothyroidism is positively associated with anxiety, while untreated hyperthyroidism is significantly related to major depressive disorder 7

Subclinical Dysfunction Matters

• Half of studies show subclinical thyroid dysfunction in anxiety patients, with blunted TSH responses to TRH stimulation and inverse relationships between anxiety levels and TSH 1, 2
• Even when baseline thyroid levels appear normal, subtle HPT axis dysfunction contributes to anxiety symptoms 6
• Higher TSH levels correlate with more severe panic attacks in non-medicated patients 8

Practical Screening Algorithm

Initial Approach

• Order TSH as the primary screening test for all patients presenting with anxiety disorders 2
• Add free T4 if TSH is abnormal or if clinical suspicion for thyroid disease is high 2
• This targeted approach avoids unnecessary extensive laboratory panels while capturing the most clinically relevant dysfunction 2

When to Suspect Thyroid Disease

• Look for physical examination findings suggesting thyroid dysfunction (tremor, tachycardia, heat/cold intolerance, weight changes, skin changes) 1
• Consider patient age, sex, BMI, and smoking status as confounding factors 1, 2
• Screen for family history of thyroid disease or autoimmune conditions 1

Treatment Implications

Optimizing Thyroid Replacement Reduces Anxiety

• The American Association of Clinical Endocrinologists recommends optimizing thyroid hormone replacement to improve anxiety symptoms, targeting TSH 0.5-2.0 mU/L for most patients 5
• Inadequate thyroid replacement causes anxiety, nervousness, irritability, and emotional lability as recognized adverse effects of under-treatment 5
• Clinical treatment of impaired thyroid function may be useful for comorbid anxiety in patients with depression 4

Common Pitfalls to Avoid

• Do not attribute all anxiety symptoms to psychiatric illness without ruling out medical causes first 2
• Do not assume normal baseline thyroid levels exclude subtle HPT axis dysfunction—consider TRH stimulation testing in refractory cases 1, 6
• Do not forget to control for depression when assessing the thyroid-anxiety relationship, as depression is a major confounder 1, 2
• Avoid treating peripheral anxiety symptoms (palpitations, tremor) with beta-blockers without first addressing underlying thyroid dysfunction 6