Ovaries and Pubertal Development

Physical Changes at Puberty

Puberty extends from the earliest signs of sexual maturation until the attainment of physical, mental, and emotional maturity. Pubertal changes in girls result directly or indirectly from maturation of the hypothalamic-pituitary-ovarian unit ( Chapter 204 ). Human puberty is characterized hormonally by a resetting of the negative gonadal steroid feedback loop, the establishment of new circadian and ultradian (frequent) gonadotropin rhythms, and the acquisition in the female of a positive estrogen feedback loop that controls the menstrual cycle as interdependent expressions of the gonadotropins and ovarian steroids. In girls, pubertal development generally occurs between 7 and 14 years of age. The age at onset and the rate of progress through puberty are variable and depend on genetic, socioeconomic, nutritional, physical, and psychological factors. Racial differences also appear to be relevant for the onset of pubertal development. For example, in the United States, pubertal development begins earlier in Black girls than in White girls.

Physical changes occur in an orderly sequence during a definite time frame in puberty ( Fig. 217-1 ). Breast budding in girls is usually the first pubertal change, followed shortly by the appearance of pubic hair, with menarche occurring late in pubertal development. The time from breast budding (mean age of 10.0 years in White girls and 8.9 years in Black girls) to menarche is 2 years. Breast development results from increasing ovarian production of estrogen, and pubic and axillary hair results from increasing androgen production. Estrogens are required for the growth of pubic hair as well.

The ovarian sex steroids join with growth hormone and adrenal androgens to produce the adolescent growth spurt. Peak growth velocity is achieved relatively early, with little growth observed after menarche. Estrogens are necessary for the normal formation, mineralization, and maturation of bones. Estrogen, not testosterone, is the primary hormone that mediates pubertal bone growth in both males and females, and more than 50 genes play roles in determining final adult height. Well-established standards exist for determining whether bone age is appropriate for chronologic age, typically by examining radiographs of the bones of the wrist. Estrogen deficiencies retard, and excesses advance, bone age in relation to chronologic age.

Lean body mass, skeletal mass, and body fat are equal in prepubertal boys and girls, but by maturity, women have twice as much body fat as men but have less lean body mass and skeletal mass as a result of differences in sex steroids.

Hormonal Changes

The ovaries function even in early childhood. Levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are normally low, and these levels increase if the ovaries are removed before puberty, just as they do later in life, thereby indicating the exquisite sensitivity of the hypothalamic-pituitary unit to extremely low circulating sex steroid levels. As puberty nears, a progressive decrease in the sensitivity of the hypothalamic-pituitary unit to sex steroids leads to the increased secretion of pituitary gonadotropins, stimulation of sex steroid output, and development of secondary sex characteristics. Increased secretion of both LH and FSH initially occurs at night with sleep and is associated with increased estradiol secretion the next morning ( Fig. 217-2 ). As is true for most hormones, LH and FSH are secreted in an episodic or pulsatile rather than a continuous fashion ( Chapter 205 ). Later in puberty, secretion of LH and FSH is increased throughout the 24-hour period, except during the early follicular phase, when nighttime increases still occur. Basal levels of estradiol, the major estrogen secreted by the ovaries, increase throughout puberty. A “critical body mass” may be required for positive estrogen feedback and ovulation. During the first 2 years after menarche, up to 90% of menstrual cycles may be anovulatory because of a delay in synchronization of the hypothalamic-pituitary-ovarian axis.

Ovarian Cysts and Adnexal Masses

Follicular growth, resulting in an ovarian cyst, is an expected finding during the reproductive years. However, palpable masses before or after the reproductive years require thorough investigation to exclude various cancers ( Chapter 184 ). A pelvic mass during the reproductive years could represent an ovarian cyst, but could also represent an endometrioma, ovarian fibroma, intrauterine pregnancy, ectopic pregnancy ( Chapter 218 ), uterine fibroid (Chapter 184), tubo-ovarian abscess ( Chapter 264 ), peritubal cyst, or less likely, ovarian or tubal cancer. History, physical examination, pregnancy test, and pelvic ultrasound would assist in focusing the differential diagnosis. CA-125 during the reproductive years is nonspecific and should not be used to exclude ovarian cancer ( Chapter 184 ). Incidentally detected adnexal lesions are found in approximately 4 to 5% of women undergoing computed tomography (CT) scan and in 9 to 10% undergoing ultrasound. The overwhelming majority of these masses are benign, and magnetic resonance imaging (MRI) can decrease the rates of resection or oophorectomy for benign lesions.