Thyroid Panel (TSH, fT4, fT3, antibodies)

•Observational— Standard endocrine practice

Screening with TSH

TSH is the most sensitive thyroid test in primary hypothyroidism or hyperthyroidism because the pituitary amplifies small thyroid hormone changes. For routine screening, TSH alone is sufficient.

When to add free T4, free T3, antibodies

• TSH abnormal → add free T4 to confirm.
• Symptoms of hypo- or hyperthyroidism with normal TSH → check fT4 and fT3 (especially for sick euthyroid, conversion issues).
• Autoimmune thyroid disease screening → TPO antibodies.
• Subclinical disease → antibody status guides whether to monitor or treat.

Subclinical disease

• Subclinical hypothyroidism: TSH 4.5–10 with normal fT4. Treatment benefit unclear unless pregnancy planning, very high TSH, or positive TPO + symptoms.
• Subclinical hyperthyroidism: TSH <0.4 with normal fT4/fT3. Risk of atrial fibrillation and osteoporosis in older adults; usually treated.

Hashimoto’s

The most common autoimmune cause of hypothyroidism. TPO antibodies are the marker. Lifestyle factors (selenium adequacy, gluten in some patients, iodine excess) can modulate progression but treatment is levothyroxine.

T3 supplementation debate

Most patients do well on levothyroxine (T4 only). A minority of hypothyroid patients feel better on T4+T3 combinations (Liothyronine or NDT). Evidence is mixed.

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Cognitive decline, Cortisol, Atrial fibrillation, Osteoporosis.