What laboratory value is most often missed or under‑recognized in adults with chronic psychiatric (mental‑health) disorders?

Thyroid Function (TSH) is the Most Commonly Missed Laboratory Value in Chronic Mental Health Patients

Thyroid-stimulating hormone (TSH) is the single most under-recognized laboratory value in adults with chronic psychiatric disorders, with studies showing 5-17% of psychiatric patients have thyroid dysfunction that directly contributes to or exacerbates their mental health symptoms. 1, 2

Why Thyroid Testing is Critical Yet Overlooked

High Prevalence of Thyroid Dysfunction in Psychiatric Populations

• Thyroid abnormalities occur in 7.8-17% of hospitalized psychiatric patients, far exceeding the rate detected by routine clinical examination alone 3
• Among patients with abnormal thyroid tests, 5 out of 10 cases had their mental illness directly related to thyroid dysfunction, particularly in affective disorders 1
• Primary hypothyroidism can cause acute mania and psychiatric symptoms that are often misattributed to primary psychiatric illness 4
• Patients with elevated TSH have 10.7 days longer hospital stays compared to those with normal values, indicating significant clinical impact 3

The Clinical Disconnect

• Despite this high prevalence, thyroid testing is recommended as one of the few selective screening tests that should be performed, yet it remains frequently omitted 1
• History and physical examination alone miss thyroid disease in psychiatric patients because symptoms overlap significantly with psychiatric presentations 2, 5
• The American College of Emergency Physicians specifically identifies TSH as a targeted test that should be obtained when affective disorder presents with clinical signs of thyroid disease 2

When to Check TSH in Psychiatric Patients

High-Risk Populations Requiring TSH Testing

• Elderly patients (≥65 years) presenting with psychiatric symptoms 6
• Patients with affective disorders (depression, mania, bipolar disorder) 1, 7
• Patients with substance abuse history who have higher rates of metabolic derangements 6, 4
• New-onset psychiatric symptoms without prior psychiatric history 2
• Patients with treatment-resistant psychiatric symptoms 5, 3

Specific Clinical Indicators

• Check TSH when patients present with depression combined with fatigue, weight changes, or cold intolerance 2, 5
• Order TSH in manic patients, as primary hypothyroidism paradoxically can cause acute mania 4
• Test in patients with prolonged psychiatric hospitalizations or poor treatment response 3

Critical Pitfalls to Avoid

Common Errors in Thyroid Assessment

• Do not rely on clinical examination alone to rule out thyroid disease—symptoms are too non-specific in psychiatric populations 2, 5, 8
• Do not assume psychological distress causes thyroid symptoms—54% of patients referred for thyroid testing have high psychological morbidity, but this does not predict thyroid dysfunction 8
• Do not order only T4 or free T4—TSH is the most sensitive first-line test, with abnormalities detected in 7.8% of cases versus only 1.3% for free T4 3
• Do not ignore elevated TSH even when T4 is normal—subclinical hypothyroidism (elevated TSH with normal T4) affects 5-10% of adults and contributes to psychiatric symptoms 8

Interpretation Challenges

• Acute psychiatric decompensation can cause transient TSH elevations that normalize within 7-21 days, so consider repeat testing if initial values are abnormal 5, 9
• Psychiatric illness itself can suppress TSH or cause elevated T4, creating false impressions of thyroid disease 5, 9
• Use sensitive TSH assays as the first-line test rather than TRH stimulation testing, which has low sensitivity and specificity 5

Practical Testing Algorithm

For Alert, Cooperative Patients with Normal Vital Signs

• Check TSH selectively based on clinical indicators (affective disorder, elderly age, treatment resistance) rather than as routine blanket testing 1, 2
• If TSH is abnormal, obtain free T4 to distinguish overt from subclinical hypothyroidism 5, 3
• Repeat abnormal TSH in 1-3 weeks to distinguish transient stress-related changes from true thyroid disease 5, 9

For High-Risk Patients

• In elderly patients, those with substance abuse, or new psychiatric presentations, include TSH in the targeted laboratory evaluation alongside comprehensive metabolic panel and glucose 6, 4
• For patients with polysubstance use disorder and schizophrenia, TSH should be part of the essential workup given the 30% rate of organic causes 4

Why Other Tests Are Less Commonly Missed

• Glucose and electrolytes are more readily ordered because acute metabolic derangements present with obvious vital sign abnormalities 2, 4
• CBC is commonly obtained when infection is suspected based on fever 2, 6
• Urine drug screens are frequently mandated by psychiatric facilities, though evidence shows they have low clinical utility 1, 6
• Extensive laboratory panels (CBC, CMP, LFTs) are often over-ordered despite low yield, with false positives 8 times more common than true positives 1, 2, 6