Precocious puberty refers to the onset of pubertal changes before they would generally be expected based on a person’s age. Physicians generally define these changes as occurring approximately 2 ½ to 3 standard deviations below the average age of onset of puberty. For girls, this generally means pubertal changes happening before age 8, and in boys, before age 9.
Pubertal changes can be described as breast or pubic hair development in girls, or onset of menstruation. In boys, pubertal changes generally are reflected by testicular enlargement, growth of the penis, and development of pubic hair.
The causes of precocious puberty can be diverse. They are generally classified into two categories: gonadotropin-dependent precocious puberty (GDPP) and gonadotropin-independent precocious puberty (GIPP).
Gonadotropin-dependent precocious puberty (GDPP) refers to the onset of pubertal changes occurring at the level of the hypothalamus in the brain, releasing hormones to initiate pubertal changes. This reflects the normal changes that occur for the onset of puberty, but at an earlier age. Tumors in the brain can infrequently cause GDPP. Most often, however, the cause behind GDPP is unknown.
Gonadotropin-independent precocious puberty (GIPP) means that the hypothalamus in the brain that regulates pubertal changes is not yet turned on, and that the pubertal changes seen are the result of abnormal hormone secretion of either estrogens (female hormone) or androgens (male hormone) from a different site in the body. In GIPP, tumors of the ovary or testis can produce hormones that initiate pubertal changes. Ovarian cysts can also cause GDPP. Finally, disorders of the adrenal gland, and tumors of the adrenal gland or the pituitary gland in the brain can be a rare cause of GIPP.
Evaluation and Diagnosis
In general, girls who show signs of pubertal development before the age of 8 and boys with pubertal development before the age of 9 should be evaluated for precocious puberty. Evaluation will generally include a complete medical history and physical exam.
Other tests that may be obtained include:
- An X-ray of the hand and wrist (this evaluates whether the bone appears to be more advanced in growth than would be expected based on age, a sign of precocious puberty)
- Blood work (to see if the pubertal changes are a form of GDPP or GIPP)
If GDPP is suspected, an MRI of the brain may be obtained to look for tumors that can be a rare cause of GDPP. If GIPP is suspected, additional blood work to measure levels of estrogens and/or androgens will be obtained. If GIPP is suspected, an imaging study such as an abdominal ultrasound or CT scan may be ordered to see if the source of the increased hormone secretion can be identified.
Treatment for precocious puberty depends on its cause. If GDPP is suspected, medications can be given that will temporarily turn off the hypothalamus, thus slowing the progress of pubertal changes until a child is older. If GIPP is assumed, treatment will be directed at the source of the excess hormone secretion.
Delayed puberty is generally defined as the absence or incomplete development of secondary sexual characteristics by an age at which 95% of children have initiated sexual development. Development of secondary sexual characteristics initially includes breast development in girls, and an increase in testicular size in boys. Using this definition, the beginning of breast development should be seen in girls by age 12, and testicular growth in boys by age 14.
Delayed puberty can be related to a variety of causes. Normally, pubertal changes are initiated by secretion of a hormone called GnRH (gonadotropin releasing hormone) from a part of the brain called the hypothalamus. This secretion of GnRH can be impaired by many causes, such as chronic or acute illnesses, malnutrition, eating disorders, thyroid problems, congenital abnormalities, or, more rarely, from tumors. Occasionally, secretion of GnRH from the hypothalamus to initiate puberty is delayed for no apparent reason, which is termed constitutional delay.
Next, problems can arise in the gonads (the ovaries in girls and testes in boys). Generally, the ovaries secrete a hormone called estradiol, and the testes secrete testosterone, which initiate secondary sexual development. Oftentimes, problems with the gonads can be related to chromosomal abnormalities. Finally, in girls who initiate normal pubertal changes such as breast and pubic hair development, but fail to menstruate, a developmental problem of the uterus or vagina may be the cause.
Evaluation and Diagnosis
To evaluate delayed puberty, a physician will perform a complete history and physical exam, paying attention to whether any secondary sexual development has occurred.
Breast development in girls, and genital development in boys, and pubic hair development in both boys and girls can be classified based on Tanner staging. Tanner stage I generally indicates no development, whereas Tanner stage 5 indicates normal adult development.
Next, physicians will often obtain blood work to look at hormones secreted by the pituitary gland in the brain (FSH and LH) in response to GnRH secretion from the hypothalamus. This helps determine whether the problem in pubertal development is at the level of the hypothalamus or the gonads (the ovaries or testes).
Additional testing that may be obtained includes:
- Blood work to look at thyroid function and prolactin levels (another pituitary hormone)
- Estradiol or testosterone levels (if problems with the ovary or testis are suspected)
- Pelvic ultrasound (if developmental problems of the uterus or vagina are suspected)
- A karyotype (if a chromosomal abnormality is suspected)
Treatment will depend on the underlying etiology for the delayed puberty. In certain situations, hormonal replacement may be started.