Macroscopic changes in the mammary glands of healthy cats after progestogen administration

The administration of contraceptives in female cats leads to problems such as pyometra, fetal maceration, mammary hyperplasia, and mammary neoplasms. Among the diseases caused by contraceptives, mammary hyperplasia has only been diagnosed in felines. However, few experimental studies have shown that contraceptive administration can cause feline mammary hyperplasia. This study aimed to evaluate the effects of the administration of a single dose of contraceptives in the mammary glands of healthy cats. Twenty cat owners who had administered contraceptives to female cats were selected. Animals were divided into two groups. Contraceptives were administered to cats in the first group, and saline solution was administered to cats in the other group (control). Before drug administration, all cats were clinically examined. Anamnesis, physical examination, blood count, biochemical tests, and abdominal ultrasonography were performed. Thirty days after the administration of contraceptives, all cats were examined, and the examinations were repeated. At 30 days, no changes were observed in the blood count or ultrasound findings. However, upon physical examination, all cats that received contraceptives showed generalized enlargement of their mammary glands. Cats in the control group were clinically normal. Ninety days after the procedure, the cats underwent an ovariohysterectomy. At that time, all cats were clinically normal and mammary enlargement regressed. It was concluded that a single contraceptive application could cause macroscopic mammary changes suggestive of hyperplasia in ten cats.