Precocious puberty: Making the distinction between common normal variants and more serious problems

DR. KAPLOWITZ is chief of endocrinology at Children's National Medical Center, Washington, D.C.

The author has nothing to disclose in regard to affiliations with, or financial interests in, any organization that may have an interest in any part of this article.

During the past decade, precocious puberty, particularly in girls, has emerged as a hot topic as reports arose that normal girls are maturing earlier than they did in the past. In this article, I describe the parameters of normal puberty and delineate the important difference between early breast development and early appearance of pubic hair. I then briefly review those important studies that suggest that, in the United States, puberty is indeed beginning earlier, and discuss common normal variants that may be confused with precocious puberty.¹ Last, I offer guidance to you, the generalist pediatrician, on how to distinguish those normal variants from the less common situations that typically merit extensive evaluation and treatment.

The defining hormonal event of puberty is activation of the hypothalamic pituitary gonadotropin (HPG) axis, in which increased pulsatile secretion of gonadotropin-releasing hormone (GnRH) results in pulsatile secretion of the pituitary hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Increasing pulses of LH activate gonadal production of estradiol in a girl and testosterone in a boy, whereas increasing FSH promotes maturation of germ cells and enlargement of the ovaries and testes. In a girl, the first sign of puberty is thelarche (breast budding) and enlargement of the nipples and areola; the growth spurt occurs soon thereafter. (Assessment of thelarche in an overweight or obese girl can be achieved by palpation to distinguish firm glandular breast tissue from surrounding adipose tissue.)

The appearance of pubic and axillary hair as a sign of pubertal maturation is widely misunderstood. It is unrelated to activation of the HPG axis but, instead, results from a developmental increase in adrenal androgen production-adrenarche-that often occurs at about the same time as gonadarche. A characteristic axillary odor is also usually noted at this time. In a girl, pubic hair may appear years before thelarche occurs (parents of a 6-year old with pubic hair can be assured that their daughter will not begin her period in the second or third grade).

How young is too young for puberty?

Some, including this author, have proposed lowering-to 7 years in white girls and 6 years in African-American girls-the age at which appearance of breast tissue or pubic hair is considered precocious.⁶ Others have argued that, first, adjusting the age range would increase the risk that serious pathology is missed and, second, the fact that girls are maturing earlier does not confer normalcy on early maturation. It has also been recognized that the rate of progression of early breast development is quite variable, and that some girls have a slow or non-progressive variant of precocious puberty. A girl whose breasts develop at 8 years and who reaches Tanner stage 3 within six months is a more worrisome problem than the girl who has breast budding at 7 years but shows normal growth and little or no change over the next six months.

No recent increase in the number of boys entering puberty before 9 years has been reported; there is, therefore, little reason to consider a change to the age at which puberty in males is considered precocious.

Common normal variants, and their management

Premature adrenarche, the early appearance of pubic or axillary hair, or both, without other signs of puberty, is caused by an earlier-than-normal increase in secretion of adrenal androgens. Premature adrenarche, more common in girls than in boys, accounted for 46% of patients in my retrospective study of 104 referrals for precocious puberty.⁷ Most affected children have characteristic axillary odor. Although growth is usually normal, I have found growth acceleration (along with advancement of two or more years in bone age) in one sixth of cases.⁷ The only consistent hormonal finding is an elevated level of the major circulating adrenal androgen, dehydroepiandrosterone sulfate (DHEA-S).

No laboratory studies or bone-age studies are necessary in a child who is growing at a normal rate and in whom the only findings are body odor and pubic or axillary hair growth. Simply monitor the child; if the growth rate remains normal and the amount of pubic hair is not increasing rapidly, referral is usually unnecessary.