Premature onset of pubertal changes.
So-called isosexual precocious puberty is usually defined
as onset of menarche in the female before age 8.5 years or pubertal changes
in the male before age 10 years. Schedewie et al. (1981) and Rosenthal et
al. (1983) also described a syndrome of sexual precocity in boys,
characterized by a sex-limited autosomal dominant inheritance pattern and
extremely rapid virilization, where increased gonadal testosterone secretion
appears to be gonadotropin-independent (male-limited precocious puberty or
familial male precocious puberty).
In 80 to 90% of girls and approximately
50% of boys with precocious puberty, no causative factor can be found.
Precocious puberty is a more frequent occurrence in females than in males,
but familial occurrence seems rarer in females. In males, sex-limited
autosomal dominant inheritance was postulated, with the trait transmitted
only by affected males to half their sons. In the syndrome of male-limited
precocious puberty, the disorder is caused by constitutively activating
mutations of the luteinizing hormone receptor gene.
There is a premature activation of the
hypothalamic-pituitary-gonadal axis as shown by increased secretion of
luteinizing hormone and follicle-stimulating hormone. In male-limited
precocious puberty, testicular Leydig cell hyperplasia is observed and the
resultant virilization results from increased secretion rather than
decreased clearance of gonadal testosterone.
Levels of plasma follicle-stimulating hormone and
luteinizing hormone are elevated for the age of the patient. Plasma
testosterone (in boys) and estradiol (in girls) are usually elevated to
levels consistent with the stage of puberty and osseous maturation. In the
syndrome of male-limited precocious puberty, both basal and
gonadotropin-releasing hormone-induced secretion of luteinizing hormone is
low and there are no suppressive effects of potent gonadotropin-releasing
hormone analogues. Advanced spermatogenesis is confirmed on testicular biopsy.
Extremely variable clinical course. Puberty may
occur before 3 years of age. Affected children may complete sexual
maturation rapidly or slowly. Adult height is reduced as the increased rate
of ossification results in early closure of the epiphyses. Dental age and
mental development are usually compatible with chronologic age.
Hypothyroidism is occasionally accompanied by precocious puberty and thyroid function
should be checked and if it is the case, treatment should be administered in these patients.
Otherwise, treatment consists mainly of psychological support of the patient and family.
Sexual precocity, fibrous dysplasia, and patchy pigmentation
occur in McCune-Albright syndrome where hyperthyroidism is common. Precocious puberty may
also result from organic brain lesions such as hypothalamic hamartomas. Signs of
increased intracranial pressure may surface years later. Computed tomography scan of the head is
indicated in all boys with true precocious puberty when no specific cause can be found.
In boys, other causes of the precocity should be evaluated, including adrenogenital
syndrome, Leydig cell tumor, and gonadotropin-producing hepatoma.
In patients in whom precocity arises
as the result of intracranial lesions, examine for signs of increased
intracranial pressure. Determine thyroid function status; patients on
thyroxine replacement for hypothyroidism should have the therapy ...