Hyperestrogenism (Estrogen Excess) – Disorders with Hair Loss in dogs

Hyperestogenism is caused by the overproduction of estrogen from the ovaries or testicles. In females, it is associated with granulosa cell tumors and cysts of the ovaries. In males, it is caused by testicular tumors.

Signs of hyperestrogenism are feminization with enlargement of the mammary glands and nipples in both sexes, enlargement of the vulva and clitoris in females, and the develoment of a pendulous prepuce in males. Females may have irregular heat cycles, false pregnancy, and pyometra.

Skin and coat changes begin in the perineum around the genital areas and proceed to the underside of the abdomen. Typically, the hair becomes dry and brittle, falls out easily, and fails to regrow. Later the skin becomes darkly pigmented. A dry, flaky seborrhea often develops, particularly in females. The coat and skin changes follow a symmetrical pattern.

The cause of the hyperestrogenism should be determined by physical examination, ultrasound, endocrine blood tests, and, if necessary, laparoscopy or exploratory surgery.

Treatment: Hyperestrogenism in both sexes responds well to neutering.