[Influence of thyroid function in CPK serum levels].

OBJECTIVE To determine serum CPK variation based on TSH e free T4 (FT4), and to assess serum CPK in pathological states of the thyroid (hyperthyroidism and hypothyroidism), in relation to the euthyroidism. MATERIAL AND METHODS We evaluated retrospectively 6,230 laboratory results of TSH and CPK from 2007 to 2011. From these, 3,369 had free T4 results. We evaluated the correlation between CPK and TSH and the pathological states of the thyroid. RESULTS The correlation between TSH and CPK was positive (r = 0.065), while that between CPK and FT4 was negative (r = -0.091, p < 0.05). From the total of results analyzed, 586 (9.4%) were measures of hyperthyroidism, with a median (range) of CPK of 98 U/L (27 to 1,113), and 556 (8.9%) were of hypothyroidism, with CPK of 114 U/L (25-4,182). CONCLUSION A positive correlation was found between serum CPK and TSH, and a negative correlation between CPK and FT4. CPK was lower in the group with hyperthyroidism, and greater in that with hypothyroidism.