Population data indicate that thyroid regulation is consistent with an equilibrium-point model, but not with a set-point model

Although it is believed that normal thyroid hormone levels are set points, representing individually pre-determined reference levels, in this paper, we discuss how analysis of the population distribution of Free Thyroxine/Thyroid Simulating Hormone (FT4/TSH) levels supports a model of homeostasis in which these levels represent the equilibrium points of the physiologic processes of homeostasis alone