Central hypothyroidism (CeH) is a rare disease caused by impaired production of thyroid-stimulating hormone (TSH), usually associated with multiple pituitary hormone deficiencies. Antidepressants have been proposed as a potential cause of an isolated form of CeH, but evidence is scarce. Here, we describe a case of a 58-year-old male with isolated low free thyroxine (fT4) and inappropriately normal TSH levels, diagnosed during treatment with duloxetine. No pituitary or thyroid disease was identified, and imaging studies were unremarkable. After exclusion of alternative causes, low-dose levothyroxine (LT4) was initiated. Following the gradual discontinuation of duloxetine and LT4, thyroid function fully normalized and remained stable at follow-up. The temporal relationship and reversibility support a possible causal role of duloxetine in inducing CeH. Although the underlying mechanisms remain unclear, this case highlights the need to consider drug-induced CeH in patients receiving antidepressants. Further studies are needed to confirm this rare association and its clinical implications.
Villanova et al. (2026) studied this question.