Effect of sex steroids on soleus muscle response in hypocalcemic medium (in vitro).

Purpose: Postoperative hypocalcemia is a frequently encountered complication of thyroid surgery. Since hypocalcemic symptoms are closely associated with sex, the aim of this study is to investigate the effects of sex steroids on muscle tissue under hypocalcemic conditions.

Methods: Six groups consisting of control male (M), control female (F), gonadectomized male (M-), gonadectomized female (F-), estradiol-applied gonadectomized male (MX), and testosterone-applied gonadectomized female (FX) rats were used. Contraction recordings were obtained from soleus muscle flaps. Maximal tension (PT), frequency required for 50% of PT (F50), contraction velocity at F50 (V50), and changes in contraction values (d[PT], d[F50], d[V50]) between normocalcemic and hypocalcemic conditions were calculated.

Results: d[PT], d[F50], and d[V50] were significantly higher in M- and MX groups compared with control M group. Whereas d[PT], d[F50], and d[V50] parameters of the F- group were significantly higher than control F group, d[F50] and d[PT] of the FX group showed no significant change and d[V50] for the FX group was significantly lower. A comparison of control groups showed that d[PT], d[F50], and d[V50] of the F group were significantly higher than those of the M group.

Conclusion: Whereas absence of both testosterone and estradiol caused an increase in hypocalcemia-induced changes in contraction parameters of rat skeletal muscle, presence or application of testosterone clearly stabilized contraction parameters.