Measurement of basal gonadotropin levels is the first step in the evaluation of a child with sexual precocity (Fig. 29.16).
2.
Thyroid function should be evaluated to rule out primary hypothyroidism as the cause of precocious development.
3.
High levels of LH (which really may be human chorionic gonadotropin detected because of cross-reactivity with LH in immunoassays) suggest a gonadotropinproducing neoplasm, most often a pinealoma (ectopic germinoma) or choriocarcinoma or, less often, a hepatoblastoma. (Gonadotropin-producing neoplasms are the only causes of precocious puberty in which the gonadotropin dependence does not equate with central precocious puberty.) 4.
Low or pubertal levels of gonadotropins indicate the need to determine circulating estradiol concentrations in girls with isosexual development and to assess androgen levels, specifically testosterone, DHEAS, and 17α-hydroxyprogesterone in girls with heterosexual development.
5.
Increased estradiol levels suggest an estrogen-secreting neoplasm, probably of ovarian origin.
6.
Increased testosterone levels suggest an androgen-producing neoplasm of the ovary or the adrenal gland. Such neoplasms may be palpable on abdominal or rectal exam ination. Increased 17α-hydroxyprogesterone levels are diagnostic of 21-hydroxylase deficiency (i.e., congenital adrenal hyperplasia [CAH]). Levels of DHEAS are elevated in various forms of CAH.
7.
If the estradiol levels are compatible with the degree of pubertal development observed, evaluation of the central nervous system by MRI or CT scanning is warranted.
8.
Bone age should always be assessed in evaluating an individual with sexual precocity.
9.
A GnRH stimulation test can be used to confirm central precocious puberty. After 100 μg GnRH, an LH peak of greater than 15 mIU/mL is suggestive of gonadotropin-dependent precocious puberty (68).
Perhaps the most difficult decision for the gynecologist is determining how much evaluation is warranted for the young girl brought in by her mother for precocious breast budding only (precocious thelarche) or the appearance of pubic or axillary hair alone (precocious pubarche or adrenarche) (Fig. 29.17). In such cases, it is acceptable to many clinicians to follow the patient at frequent intervals and to proceed with evaluation if there is evidence of pubertal progression. The feasibility of this approach may depend on the concerns of the parents.
Premature Thelarche Premature thelarche is unilateral or bilateral breast enlargement without other signs of sexual maturation. There is no significant nipple or areola development. It usually occurs by 2 years of age and rarely after age 4. It may be caused by increased sensitivity of the breasts to low levels of estrogen or to increased estradiol secretion by follicular cysts. It is a benign self-limited disorder and thus only reassurance and follow-up are required. In most cases, onset of puberty, adult height, and adult reproductive function are normal (69). Rarely, premature thelarche can be a harbinger of progressive gonadarche. It is suggested that measurement of uterine volume (anteroposterior diameter × longitudinal diameter × transverse diameter × 0.523) may be the most sensitive and specific discriminator between premature thelarche and early true precocious puberty (70). If needed, breast ultrasound can help distinguish unilateral premature thelarche from fibroadenomas, cysts, neurofibromas, or other lesions.