TG and hypothyroidism: The clinical manifestation includes reduced responsiveness of the targeted tissues (pituitary and/or surrounding) to thyroid hormone, which leads to increased concentrations of free thyroxine (FT4) and triiodothyronine (FT3), but normal or slightly increased serum thyrotropin (thyroid-stimulating hormone [TSH]) levels that result in the appearance of symptoms of hyper- or hypothyroidism.