Causes
Delayed puberty in boys is defined as lack of testicular enlargement (>4 mL) by age 14 and is due to the inadequate secretion of testosterone required for normal pubertal development. Hypogonadism may be classified as primary due to gonadal failure or, more commonly, secondary due to impaired GnRH (hypogonadotropic hypogonadism).
The most common cause of delayed puberty and hypogonadism is constitutional delay. Late maturation of the hypothalamic-pituitary-gonadal axis results in a delayed bone age and short stature (<3rd percentile) but normal growth velocity. Other causes of hypogonadotropic hypogonadism may be functional (eg, chronic illness, malnutrition, stress), genetic (eg, Kallmann syndrome), or due to hypothalamic/pituitary pathology (eg, craniopharyngioma).
This adolescent is showing signs of hypogonadism, including prepubertal testes and absent facial and pubic hair. He is also below average height due to a delayed pubertal growth spurt. A bone age radiograph is indicated to assess remaining growth potential and, although delayed, he does not have short stature or a family history of "late bloomers" as expected with constitutional delay. Therefore, further testing to exclude pathologic etiologies is necessary.
Initial evaluation includes FSH, LH, and testosterone levels to differentiate between primary (elevated FSH/LH) and secondary (low to normal FSH/LH) hypogonadism. Prolactin and TSH tests should also be ordered, as increased levels interfere with GnRH secretion.
Normal:
Breast development (thelarche) is typically the first sign of puberty in girls and occurs at age 8-12 in response to rising estrogen levels. Pubic hair development (pubarche) usually follows thelarche but can occur first. The onset of menses (menarche) is expected around Tanner stage 4, approximately 2-2.5 years after initial breast bud development. The average age for menarche is 12.5; however, lack of menses is considered normal at age <15 if development of secondary sex characteristics has been appropriate. In the 6 months preceding menarche, girls experience a growth spurt, a peak in growth velocity.
Tits, pits, mits, lips (breast, hair, growth, menarche)
Pelvic ultrasound and a FSH level are ordered to evaluate for primary amenorrhea, the lack of menses at age >15 with secondary sexual characteristics (eg, breast development) or age >13 with no secondary sexual characteristics.