The Smallest Kid in School: Evaluating Delayed Puberty

Peter A. Lee, MD, PhD; Christopher P. Houk, MD


August 13, 2012

What Is Delayed Puberty?

Puberty is a complex process involving the interplay of hypothalamic, pituitary, and gonadal hormones. It is the phase of growth in which secondary sexual characteristics develop and linear growth is accelerated, and it marks the transition between childhood and adulthood.

GnRH-secreting neurons migrate from the embryonic olfactory placode to the human forebrain during fetal life. A network of these neurons within the hypothalamus acts in concert to produce pulsatile GnRH release. The resulting pubertal onset increases pituitary LH and FSH release, which in turn stimulates gonadal sex-steroid production. Gonadotropins stimulate testicular or ovarian development; gonadal sex steroids then stimulate development of secondary sexual characteristics.

Defining Delay

Delayed puberty is defined as an absence of secondary sexual characteristics at an age that is greater than 2.5 standard deviations above the mean. The absolute age varies somewhat among racial/ethnic groups and is also dependent on socioeconomic conditions. In general, the upper age limit is considered to be approximately 14 years for boys and 13 years for girls.[1,2] Lack of pubertal progression after beginning at a normal time should also be considered as delayed. For boys, failure to complete puberty within 4 years indicates lack of progression; for girls, it is the failure to attain menarche 3 years after the beginning of breast development (thelarche).

There has been a secular trend toward earlier age at thelarche over recent years.[3,4,5] However, there is no clear evidence of a decreasing age at menarche.[3,6]

Physical Findings

The first sign of the onset of puberty in boys is an increase in testicular volume, generally accepted to be a volume greater than 4 cc, or testicular length greater than 2.5 cm. which indicates pubertal growth. In girls, thelarche is generally the first evidence of puberty. Palpation may be required to discriminate glandular breast tissue from fatty subcutaneous tissue on the chest. A disc of firm, tender, tissue immediately beneath the areolae is consistent with breast growth. Additional findings indicative of breast development are a pigmented areolae diameter greater than 1.5cm and/or a nipple diameter greater than 3 mm.

In boys and girls, the presence of pubic and other sexual hair growth does not always indicate onset of puberty. Hair growth may be a consequence of adrenarche, a normal physiologic event in which the adrenal gland begins to secrete dehydroepiandrosterone and androstenedione; these relatively weak androgens stimulate the development of pubic hair (pubarche), axillary hair, and adult-type body odor. Although temporally related to puberty, adrenarche develops independently of pubertal activation of the hypothalamic-pituitary-gonadal axis.