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The aim of this investigation was to study the effect of beta-adrenoceptor blockade on alterations in protein metabolism induced by administration of 3,5,3'-triiodothyronine (T3) to man. Urinary excretion of 3-methylhistidine and plasma concentrations of amino acids were measured in seven healthy subjects following 1 weeks's administration of T3 alone or T3 in combination with the selective beta 1-adrenoceptor blocking agent metoprolol or the non-selective beta-adrenoceptor blocking agent propranolol. Urinary excretion of 3-methylhistidine and plasma concentrations of valine, methionine, lysine, tyrosine, phenylalanine, isoleucine, leucine, and total essential and branched chain amino acids increased following administration of T3, probably in part reflecting accelerated muscle proteolysis. Neither metoprolol nor propranolol normalized 3-methylhistidine excretion or plasma concentrations of amino acids during T3 treatment. The results indicate that metabolic alterations induced by T3 and giving rise to enhanced 3-methylhistidine excretion and elevated concentrations of plasma amino acids are not normalized by beta-adrenoceptor blockade.

Three cases of pheochromocytoma diagnosed ante partum are reported. The first woman received phenoxybenzamine for 72 days until operation and the other 2 were given the drug for 2 and 3 days, respectively. Healthy infants were delivered by cesarean section followed by removal of the pheochromocytomas. The 29 cases reported in the literature of pheochromocytoma diagnosed ante partum and treated with alpha-receptor blockade are reviewed with respect to results of treatment. It is concluded that pheochromocytoma diagnosed during the 1st trimester is probably best managed by tumor resection as soon as possible. In order to avoid the risk of abortion during surgery in cases diagnosed in the 2nd trimester, the patient may well be brought to term under adequate treatment with an alpha-receptor blocking agent, when the infant is delivered by cesarean section followed by tumor removal. Third-trimester cases should be managed in the same way.