TSPO and injury: Other possible reasons include normalization of TSPO expression after an initial increase as seen after traumatic brain injury, where TSPO gene expression increases at 7 days after but returns to baseline levels at 28 days [56] and reduced binding of the radioligand to TSPO, as LHRHa may negate the multifold increase TSPO binding seen in the presence of gonadotrophins [57].