Normal menstrual cycles during adolescence occur every 21 to 45 days, with duration of bleeding up to 7 days and blood loss of 20 to 60 mL (see Chapter 533). For those whose cycles are abnormal, the most common menstrual disorders in adolescents include amenorrhea, abnormal uterine bleeding, and dysmenorrhea, which are discussed in this chapter.
Amenorrhea, the absence of menses, can be either temporary or permanent. Traditionally, there are two categories: primary amenorrhea and secondary amenorrhea. Primary amenorrhea is defined as failure to menstruate either (1) by age 15 in the presence of breast development and normal growth, (2) within 3 years of thelarche, or (3) by age 13 with the absence of secondary sexual characteristics. Also, when delay in secondary sexual development and amenorrhea exists or cyclic pelvic pain accompanies primary amenorrhea, prompt evaluation should occur.
Secondary amenorrhea is cessation of menses for greater than 3 months or 90 days. While the etiologies of primary amenorrhea are typically genetic or anatomic, all causes of secondary amenorrhea may also present as primary amenorrhea. The evaluation of infrequent menses with cycle length longer than 6 weeks is the same as amenorrhea in this discussion. See Chapter 534 for further discussion on amenorrhea in the setting of delayed puberty.
Do not overlook pregnancy, the most common cause of secondary amenorrhea, as a cause of primary amenorrhea. (See Chapter 80 for more information on the diagnosis of pregnancy.) Beyond pregnancy, the etiologies of primary and secondary amenorrhea include anatomic abnormalities or fall into three categories depending on the function of the pituitary gland in relation to the ovary: hypogonadotropic hypogonadism, hypergonadotropic hypogonadism, and eugonadotropic eugonadism. Another common classification system divides causes based on location of dysfunction within the hypothalamic–pituitary–adrenal (HPA) axis: hypothalamic, pituitary, ovarian, or other.
Hypogonadotropic hypogonadism indicates inadequate hypothalamic–pituitary stimulation of the ovary, and low levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estrogen characterize this state. Hypothalamic amenorrhea results from partial or complete inhibition of gonadotropin-releasing hormone (GnRH) release from the hypothalamus. See Table 79-1 for causes of amenorrhea characterized by hypogonadotropic hypogonadism. Excessive exercise and weight loss leading to amenorrhea may represent an eating disorder (see Chapter 76). Local lesions in the hypothalamus (eg, infiltrative processes, calcifications, gliomas, and germinomas), traumatic brain injury (TBI), and central nervous system radiation are all rare causes of GnRH deficiency. Isolated GnRH deficiency is associated with the absence (anosmia) or impairment (hyposmia) of the ability to smell (Kallman syndrome). Medications and illicit drugs may also result in amenorrhea.
TABLE 79-1Differential Diagnoses for Primary and Secondary Amenorrhea, Negative Pregnancy Test |Favorite Table|Download (.pdf) TABLE 79-1 Differential Diagnoses for Primary and Secondary Amenorrhea, Negative Pregnancy Test
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