A 29-year-old transgender woman convicted of killing a man she was dating has filed a ¥10 million lawsuit over authorities' refusal to allow hormone injections to treat her gender dysphoria in prison and at a detention center, it has been learned.

At the first trial hearing on Monday, the government asked the court to dismiss the case. The woman previously received gender reassignment surgery.

In December last year, the Tokyo District Court handed down a 16-year prison term for the murder of a man the woman was in a relationship with. She is now serving the term at a facility in the Kanto region.

According to the lawsuit, the woman has regularly received doctor-prescribed hormone injections since being diagnosed with gender dysphoria as a teenager. She later received the surgery and corrected her gender in the family register.

After her arrest in February 2015, she was allowed hormone injections while detained at a police station. But when she moved to a detention center during trial and later to prison, those treatments were withheld, as the government deemed her condition is not an illness.

Lawyers for the plaintiff say injections are necessary to maintain her hormonal balance. They argue withholding the treatment not only caused her psychological distress it also resulted in a heavier prison term as the woman was unable to fully express herself verbally during the trial.