Nervous system role of iodocompounds in blood pressure regulation

Approximately one-third of hypertensive patients with thyroid dysfunction become normotensive on restoration to the euthyroid state. Considerable evidence suggests that the nervous system is involved in these responses, but the mechanism has been obscure. New information demonstrates that iodothyronines are localized and processed in discrete neural systems in rat brain. Moreover, following a latent period, heart rate is significantly increased by intrathecal administration of triiodothyronine in a dose which sustains but does not increase heart rate when given intravenously. These observations add to existing biochemical and autoradiographic evidence that autonomic effects of iodocompounds may be mediated through direct neuroregulatory (neuromodulator and neurotransmitter) functions within the nervous system.