Adult Tph2 knockout mice without brain serotonin have moderately elevated spine trabecular bone but moderately low cortical bone thickness.

Disruption of serotonin synthesis in neurons and the periphery by knockout (KO) of mouse genes for tryptophan hydroxylases (peripheral Tph1 and neuronal Tph2) has been claimed to decrease (Tph2 KO) and increase (Tph1 KO) bone mass. In this report, adult male and female Tph2 KO mice were observed to have elevated spine trabecular bone. Female Tph2 KO mice have reduced midshaft femur cortical bone thickness. Bone mass was normal in male and female Tph1 KO mice examined as part of a Tph1/Tph2 double knockout (DKO) mouse cohort.