question: What is the role of TRH in hypertension?
answer: TRH gene overexpression induces hypertension in normal rats and spontaneously hypertensive rats have central TRH hyperactivity with increased TRH synthesis and release and an elevated TRH receptor number. TRH antisense treatment reduces hypertension.
  central TRH participates in the hypertension induced by body weight gain probably through its well-known action on sympathetic activity.
  the pressor effect of intravenous TRH is mediated primarily by a stimulation of alpha-adrenergic receptors.  Activation of cardiac beta-adrenoceptors seems to contribute to the blood pressure increasing effect of intravenous TRH. Ang II system is involved in the TRH cardiovascular effects. 
  Polymorphisms in  TRH (thyrotropin-releasing hormone) are significantly associated with both blood pressure variation and hypertension.
  TRH may mediate the central leptin-induced hypertension effect
  A parallel increase in the density of brain TRH receptors with elevation of blood pressure has been shown and suggests that brain TRH receptors may play an important role in the pathophysiology of hypertension. TRH Receptor gene participates in the etiopathogenesis of essential hypertension.