The effect of treatment of hyper- and hypothyroidism on urinary excretion of cyclic adenosine 3',5'-monophosphate. 
The urinary excretion of cyclic adenosine 3',5'-monophosphate (cyclic AMP) was examined in patients with hyperthyroidism and primary hypothyroidism, before treatment and at least six months later on return to euthyroid status.  Urinary cyclic AMP excretion was significantly greater in the hyperthyroid group than in the hypothyroid group both in the basal state (P less than 0.01) and the ambulant state (P less than 0.001).  In ambulant hyperthyroid patients absolute urinary cyclic AMP excretion (mumol/24 h) was significantly greater (P less than 0.05) prior to treatment than on return to euthyroid status.  In the hypothyroid group no significant change occurred after treatment with 1-thyroxine (P greater than 0.05).  The mechanism of changes in urinary cyclic AMP excretion in thyroid disease are discussed.