INTRODUCTION

Amenorrhea (absence of menses) can be a transient, intermittent, or permanent condition resulting from dysfunction of the hypothalamus, pituitary, ovaries, uterus, or vagina (table 1 and table 2). It is often classified as either primary (absence of menarche by age 15 years) or secondary (absence of menses for more than three cycles or six months in women who previously had menses). The menstrual cycle is susceptible to outside influences; thus, missing a single menstrual period is rarely important. In contrast, prolonged amenorrhea may be the earliest sign of a decline in general health or signal an underlying condition such as hypothyroidism.

The causes and diagnosis of secondary amenorrhea and a brief summary of treatment options are reviewed here. The etiologic and diagnostic considerations for oligomenorrhea are the same as for amenorrhea. Primary amenorrhea is discussed separately. (See "Etiology, diagnosis, and treatment of primary amenorrhea".)

ETIOLOGY

Pregnancy — Pregnancy is the most common cause of secondary amenorrhea. It may occur even in women who claim that they have not been sexually active or are positive that intercourse occurred at a "safe" time. It is also important to note that apparent menstrual bleeding does not exclude pregnancy, since a substantial number of pregnancies are associated with some early first trimester bleeding. Thus, a pregnancy test (measurements of serum or urinary human chorionic gonadotropin [hCG]) is recommended as a first step in evaluating any woman with amenorrhea. (See 'Diagnosis' below.)

Once pregnancy has been ruled out, a logical approach to women with either primary or secondary amenorrhea is to consider disorders based upon the levels of control of the menstrual cycle: hypothalamus, pituitary, ovary, and uterus. The most common causes of secondary amenorrhea are disorders of the [1,2]:

• Ovary — 40 percent
• Hypothalamus — 35 percent
• Pituitary — 19 percent
• Uterus — 5 percent
• Other — 1 percent