This paper presents a case report of a perimenopausal woman who repeatedly attended health care institutions due to chronic insomnia, and underwent pharmacological treatments and psychiatric hospitalizations without achieving any positive result for nearly three years. After compiling all the information of the case, as well as analyzing previous and recent paraclinical studies, the patient was diagnosed with hypothyroidism.The purpose of this paper is to draw attention on the adequate use of clinical diagnostic tools and processes to optimize the medical practice and to offer a better service to patients.