A transgender inmate is suing the Missouri prison system for refusing to provide hormone therapy as she transitions to a woman, adding her voice to those of prisoners in other states who argue that denying such treatment amounts to cruel and unusual punishment.

The federal lawsuit was filed last week in St. Louis on behalf of Jessica Hicklin, a 37-year old inmate serving life in prison without parole for first-degree murder. The lawsuit also names Corizon Health, the health care provider for the Missouri Department of Corrections.

A message seeking comment from the corrections department was not returned. A Corizon spokeswoman declined to comment, citing pending litigation.

The Bureau of Justice Statistics estimates there are 3,200 transgender inmates in U.S. prisons and jails.