An OB-GYN, or obstetrician-gynecologist, is a doctor who specializes in women’s health. The female body experiences many different biological functions, including menstruation, childbirth, and menopause. OB-GYNs provide care for all of this and more.
Physicians who specialize in men's sexual and reproductive health care — including the diagnosis and treatment of disorders of the male sex and reproductive organs — are called urologists. Andrology is the study of the male reproductive system, including sexual health, it is a subspecialty of urology.
In common usage, andrology pertains to men as gynecology pertains to women.