Thyroid hormone replacement for central hypothyroidism: a randomized controlled trial comparing two doses of thyroxine (T4) with a combination of T4 and triiodothyronine.

Background: Dosage of T(4) in central hypothyroidism is primarily guided by the free serum T(4) level (fT4). However, the optimum fT4 range is ill defined, and subtle hypothyroidism might be missed using this approach.

Objectives: Our aim was to investigate the effects of a body weight (bw)-adapted T(4) treatment, alone or in combination with T(3), on metabolism, well-being, and cognitive function in comparison to a regimen leading to normal fT4.