The enigma of persistent symptoms in hypothyroid patients treated with levothyroxine: A narrative review

A significant minority of patients with hypothyroidism report persistent symptoms despite achieving normal thyroid biochemistry after levothyroxine (L‐T4) replacement. Four principal lines of thinking, which are not mutually exclusive, may explain this enigma. The ‘low tissue liothyronine hypothesis’ emphasizes the potential imperfections of L‐T4 replacement therapy that may lead to hypothyroidism in some tissues such as the brain, while others...