What is a proper quick outpatient department (OPD) workup chart for an adult patient with abnormal thyroid function tests and no known medical history?

Quick OPD Workup Chart for Abnormal Thyroid Function Tests

Initial Assessment and Confirmation

Always confirm abnormal thyroid function tests with repeat testing after 3-6 weeks before initiating treatment, as 30-60% of elevated TSH values normalize spontaneously. 1

First-Line Laboratory Tests

• Measure TSH as the primary screening test with sensitivity above 98% and specificity greater than 92% 1, 2, 3
• If TSH is abnormal, measure free T4 to distinguish between subclinical (normal free T4) and overt (abnormal free T4) thyroid dysfunction 1, 3, 4
• Do not routinely measure T3 unless assessing for hyperthyroidism or T3 toxicosis, as it does not add information in hypothyroidism workup 1

Additional Diagnostic Testing

• Measure anti-TPO antibodies if TSH is elevated to confirm autoimmune etiology (Hashimoto's thyroiditis), which predicts higher progression risk to overt hypothyroidism (4.3% per year vs 2.6% in antibody-negative individuals) 1
• Check lipid profile as subclinical hypothyroidism may affect cholesterol levels 1

Clinical History - Key Elements to Assess

Symptoms Suggesting Hypothyroidism

• Fatigue, weight gain, cold intolerance, constipation, cognitive impairment, menstrual irregularities 1
• Hair loss, dry skin, bradycardia 1

Symptoms Suggesting Hyperthyroidism

• Weight loss, heat intolerance, palpitations, tremor, tachycardia, hyperactivity 5

Critical Red Flags to Identify

• Recent iodine exposure (CT contrast) which can transiently affect thyroid function 1
• Acute illness or hospitalization which can suppress TSH temporarily 1
• Medications that interfere with thyroid function (amiodarone, lithium, immunotherapy) 5, 1
• Pregnancy or planning pregnancy - requires immediate treatment at any TSH elevation 1
• Cardiac disease or atrial fibrillation - affects treatment approach and monitoring 1

Exclude Adrenal Insufficiency

• Before starting levothyroxine, rule out concurrent adrenal insufficiency especially in suspected central hypothyroidism, as thyroid hormone can precipitate life-threatening adrenal crisis 1, 6
• Check morning cortisol and ACTH if central hypothyroidism suspected 1

Physical Examination - Targeted Findings

Thyroid Gland Assessment

• Palpate for goiter, nodules, or tenderness 7
• Nodules >1 cm warrant thyroid ultrasound for further characterization 7

Cardiovascular Examination

• Check heart rate and rhythm - bradycardia suggests hypothyroidism, tachycardia/atrial fibrillation suggests hyperthyroidism 1
• Measure blood pressure - hypertension may worsen with hypothyroidism 1

Other Key Findings

• Assess for delayed relaxation of deep tendon reflexes (hypothyroidism) 1
• Check for tremor, hyperreflexia (hyperthyroidism) 5
• Look for skin changes - dry skin (hypothyroidism), warm/moist skin (hyperthyroidism) 1

Imaging - When Indicated

Thyroid Ultrasound

• Indicated for palpable nodules, goiter, or suspected thyroid cancer 5
• NOT indicated for routine workup of hypothyroidism - imaging does not help differentiate causes 5

Radioiodine Uptake and Scan

• Indicated for hyperthyroidism to distinguish Graves disease from toxic nodular goiter or thyroiditis 5
• NOT indicated for hypothyroidism - all causes show decreased uptake 5

Advanced Imaging (CT/MRI)

• NOT routinely indicated for thyroid dysfunction workup 5
• Consider neck CT with contrast only for suspected advanced thyroid cancer with extrathyroidal extension 5

Treatment Decision Algorithm Based on TSH Results

TSH >10 mIU/L with Normal Free T4 (Subclinical Hypothyroidism)

• Initiate levothyroxine therapy regardless of symptoms as this carries ~5% annual risk of progression to overt hypothyroidism 1, 6
• Starting dose: 1.6 mcg/kg/day for patients <70 years without cardiac disease 1, 6
• Starting dose: 25-50 mcg/day for patients >70 years or with cardiac disease 1, 6

TSH 4.5-10 mIU/L with Normal Free T4 (Mild Subclinical Hypothyroidism)

• Do NOT routinely treat - monitor TSH every 6-12 months 1
• Consider treatment if:
  • Symptomatic (fatigue, weight gain, cold intolerance) 1
  • Positive anti-TPO antibodies (higher progression risk) 1
  • Pregnant or planning pregnancy 1
  • On immunotherapy with symptoms 1

TSH >10 mIU/L with Low Free T4 (Overt Hypothyroidism)

• Start levothyroxine immediately without delay to prevent cardiovascular dysfunction and quality of life deterioration 1, 6
• Full replacement dose: 1.6 mcg/kg/day for patients <70 years 6
• Lower starting dose: 25-50 mcg/day for elderly or cardiac patients 6

TSH <0.1 mIU/L with Elevated Free T4 (Overt Hyperthyroidism)

• Obtain radioiodine uptake and scan to determine etiology (Graves vs toxic nodular goiter vs thyroiditis) 5
• Refer to endocrinology for definitive management 5

TSH <0.1 mIU/L with Normal Free T4 (Subclinical Hyperthyroidism)

• Repeat testing in 3-6 weeks to confirm persistence 1
• If confirmed, refer to endocrinology as treatment depends on etiology and cardiovascular risk 5

Monitoring After Treatment Initiation

During Dose Titration

• Recheck TSH and free T4 every 6-8 weeks after any dose adjustment until TSH normalizes 1, 6
• Target TSH: 0.5-4.5 mIU/L for primary hypothyroidism 1, 6

After Stabilization

• Monitor TSH every 6-12 months once stable dose achieved 1, 6
• Recheck sooner if symptoms change or new medications started 1

Critical Pitfalls to Avoid

• Never treat based on single abnormal TSH - confirm with repeat testing 1
• Never start thyroid hormone before ruling out adrenal insufficiency in suspected central hypothyroidism 1, 6
• Never assume hypothyroidism is permanent - consider transient thyroiditis, especially in recovery phase 1
• Never ignore cardiac disease - start low and titrate slowly in elderly or cardiac patients 1, 6
• Never overlook pregnancy - requires immediate treatment and closer monitoring 1, 6
• Avoid overtreatment - 25% of patients are inadvertently maintained on excessive doses causing TSH suppression, increasing risks for atrial fibrillation, osteoporosis, and fractures 1