[Alkaline phosphatase isoenzymes and hyperthyroidism].

We determined the serum total alkaline phosphatase as well as the alkaline phosphatase isoenzyme pattern in untreated and treated hyperthyreoses in the condition of euthyreosis and compared them with those of a healthy control group. The isoenzyme patterns, expressed as L/K quotient, ranged between 1.3 and 2.5 in the normal group and between 0.3 and 1.3 in the group with hyperthyreosis. The increase of the total alkaline phosphatase in hyperthyreosis was nearly exclusively conditioned by the increase of the activity of the osseous isoenzyme. The latter was increased already also then, when the total alkaline phosphatase had not transgressed the upper border of the normal. Depending on the functional condition of the thyroid gland the liver isoenzyme did not show any significant changes. In the course up to one year under thyrostatic therapy the increased activity of the osseous alkaline phosphatase decreased into the normal region as an expression of the very slowly repairing hyperthyreosis-conditioned disturbances of the osseous metabolism. An increase of the activity of the total alkaline phosphatase or of the osseous isoenzyme in the initial phase of a thyreostatic therapy of the sequel of an increase of the reactive activity of osteoblasts and must not lead to diagnostic and therapeutic uncertainties. By reason of the high sensitivity of the L/K quotient in hyperthyreoses (L/K at 95.5 % below 1.3) with a simultaneously high specifity of 89.5% the alkaline osseous phosphatase is to be discussed by all means as a helpful parameter of the peripheral function of the thyroid gland.