It is postulated that the reduced testosterone will have a negative feedback effect on the HPT axis with subsequent elevation of LH, FSH, and GnRH, but from the results of the present work, it is evident that in the PTU group, hypothyroidism has a central effect on the HPT axis due to the reduction of GnRH relative mRNA expression in brain tissue with subsequent reduced serum GnRH, LH, FSH, and testosterone, thus creating a hypo‐gonadotrophic state. The gene discussed is GNRH1; the disease is hypothyroidism.