REN and thyroid gland disorder: In order to obtain a comprehensive view on the response of the renin-angiotensin system in the hypothalamic-pituitary-adrenal axis of animals with thyroid disorders, these enzyme activities were simultaneously analyzed fluorometrically, using arylamide derivatives as substrates in hypothalamus, anterior and posterior pituitary, adrenals and plasma of euthyroid, hypothyroid, and hyperthyroid rats, and their intra- and inter-tissue correlations were evaluated.