No person shall undergo sterilization unless such person has attained the age of eighteen years and has given informed consent, in writing, to such sterilization. Whenever any physician has reason to believe a person eighteen years or over is unable to give informed consent, or when a person is in a state institution, no such sterilization shall be performed until it is determined by a probate court that the person involved is able to and has given informed consent. Whenever the court determines, under the provisions of sections 45a-690 to 45a-700, inclusive, that a person has not given informed consent, or whenever a person is under a guardianship or conservatorship, the court shall permit sterilization only upon showing that such operation or procedure is in the best interest of the person.