Futaba-kun Change!(1991)

Futaba-kun Change♡

Futaba Shimeru is a normal high-schooler living a normal life, active in his school's wrestling club and slowly getting closer to his awkward love interest, Misaki. This fails to last as he discovers his family's hereditary genetic defect that becomes active at adolescence. Although it will eventually become controllable, either excitement or stress now makes Futaba switch sex. Mayhem ensues.

(Source: Wikipedia)