Underactive thyroid: Why TSH alone isn't enough

Dr. Charalampos Romanos · April 14, 2026 · 5 min read

The thyroid is a small but crucial organ that influences our metabolism, energy, and mood. In my practice, I regularly see that thyroid dysfunction is inadequately diagnosed — often because only the TSH value is measured.

Symptoms of underactive thyroid

Patients report fatigue, weight gain, hair loss, dry skin, cold intolerance, concentration problems, and depressive moods. These symptoms develop gradually and are often not associated with the thyroid.

Why TSH alone is not enough

TSH is only one marker. Comprehensive diagnostics requires measuring free T4 (fT4), free T3 (fT3), and antibodies (TPO, thyroglobulin). Hashimoto's thyroiditis, for example, is often missed if only TSH is checked. That's why I use a comprehensive panel in functional medicine.

The central role of T3

Many patients still feel unwell even with normalised TSH and fT4. This is often due to insufficient T3 (the biologically active form). I therefore always measure fT3 and explain to my patients that T3 is crucial for energy and metabolism.

Autoimmune thyroid disease

Hashimoto's thyroiditis is an autoimmune disease and the most common cause of underactive thyroid. Testing for antibodies is essential. In addition to hormone replacement therapy, I also recommend lifestyle measures and selenium supplementation.

Optimal dosing and monitoring

The right dose is not simply a normal TSH value — it is individual. I listen to my patients: if they feel unwell despite normal TSH, I adjust the dosage. This is part of my personalised treatment approach in preventive medicine.

Long-term care and prevention

Underactive thyroid requires regular monitoring. I recommend six-monthly or annual blood tests, depending on the course. Early diagnosis and optimally adjusted therapy prevent complications and improve quality of life.