The relationship between serum testosterone level and Hoffmann reflex from the long flexor thumb muscle in...

The relationship between serum testosterone level and Hoffmann (H) reflex from right to left thumb flexors was studied in right-handed young men and women. The subjects were divided into two subgroups: fast and slow in right-hand skill, but no difference in left-hand skill (peg moving). The mean serum testosterone level was found to be significantly lower in subjects with fast right hand than those with slow right hand. The mean H reflex from right was significantly smaller in subjects with fast right hand than those with slow right hand. There was a negative, linear relationship between serum testosterone level and amplitude of H-reflex from right thumb. This was more pronounced in females than males. The H reflex from left was not significantly associated with serum testosterone levels. It was concluded that testosterone may affect the somatomotor system of the left brain during adolescence impairing the right-hand skill especially in females. These results also appear to be in accord with the testosterone theory of cerebral lateralization.