What to watch with FT4 and weight loss?

FT4 (free thyroxine) is a thyroid hormone that regulates metabolism. During weight loss, FT4 levels can change due to caloric restriction, altered binding proteins, or adjustments in thyroid medication. Low FT4 (hypothyroidism) may hinder weight loss, while high FT4 (hyperthyroidism) increases basal metabolic rate but carries risks like palpitations and muscle wasting. Importantly, FT4 alone is insufficient – TSH and possibly fT3 should also be assessed. The evidence is based on general medical practice, not on specific studies from the provided context. If weight loss stalls or is unexplained, a doctor should evaluate thyroid function. Caution: using thyroid hormones for weight loss is dangerous and not medically indicated.