What is the evaluation and treatment approach for a 13-year-old male with delayed puberty, presenting with no axillary (armpit) or pubic hair?

Evaluation and Management of Delayed Puberty in a 13-Year-Old Male

This 13-year-old boy requires immediate hormonal evaluation to distinguish between constitutional delay of growth and puberty (CDGP) versus pathologic hypogonadism, as the absence of any pubertal signs at age 13 warrants investigation even though it falls within the upper limit of normal for males.

Initial Assessment

Clinical Evaluation

• Document Tanner staging for pubic hair and testicular volume—the absence of both axillary and pubic hair suggests pre-pubertal status (Tanner stage 1) 1
• Measure testicular volume: Normal puberty in boys begins with testicular enlargement (≥4 mL or ≥2.5 cm length); absence indicates lack of pubertal onset 2
• Obtain growth velocity and bone age via hand/wrist X-ray to assess skeletal maturation and predict final height 1
• Screen for chronic illness: Ask about recurrent infections, gastrointestinal symptoms, respiratory problems, chronic anemia, or eating disorders that could delay puberty 3
• Family history: Document any familial pattern of delayed puberty, which strongly suggests CDGP 4, 2

Laboratory Workup

• Baseline hormones at age 13-14: Measure FSH, LH, and testosterone to differentiate hypogonadotropic (low gonadotropins) from hypergonadotropic (elevated gonadotropins) hypogonadism 1, 5, 6
• If gonadotropins are elevated: This indicates primary testicular failure (hypergonadotropic hypogonadism) requiring endocrine referral 2, 6
• If gonadotropins are low/normal: Consider CDGP versus hypogonadotropic hypogonadism; may require MRI of sella if concerning features present 1, 2

Diagnostic Considerations

Constitutional Delay (Most Common)

• CDGP is a diagnosis of exclusion and more common in boys than girls 2, 6
• Characterized by delayed bone age, family history of late puberty, and eventual spontaneous progression 4, 2
• Current research suggests distinct genetic profiles may help differentiate CDGP from congenital hypogonadotropic hypogonadism 2

Pathologic Causes to Exclude

• Hypogonadotropic hypogonadism: Gonadotropin or LHRH deficiency, pituitary-hypothalamic injury from tumors, trauma, or radiation 4
• Hypergonadotropic hypogonadism: Primary testicular failure from cryptorchidism, bilateral torsion, orchitis, vanishing testis syndrome, or orchidectomy 4, 6
• Chronic systemic illness: Malnutrition, chronic disease, medications (especially glucocorticoids), or emotional deprivation 1, 3

Treatment Approach

When to Treat

• Consider treatment if: The patient or family is distressed by the delay, bone age assessment is appropriate, and pathologic causes have been excluded 1, 4
• Timing: Treatment should ideally begin between ages 11-13 years to facilitate positive psychosocial adaptation, though boys typically start later than girls 5

Testosterone Therapy for CDGP

• Initial regimen: Low-dose testosterone enanthate intramuscularly for a short course of 3-6 months to stimulate pubertal development 4, 2
• Monitoring: Assess every 6 months with hand/wrist X-rays to evaluate bone age and epiphyseal closure, watching for spontaneous resumption of endogenous puberty 4, 2
• Escalation: If CDGP is confirmed and spontaneous puberty begins, discontinue exogenous testosterone; if hypogonadism is confirmed, continue with escalating doses mimicking normal puberty until completion of development 4, 2

For Confirmed Hypogonadism

• Long-term replacement: Testosterone replacement therapy will be required throughout adolescence and into adulthood for development and maintenance of secondary sexual characteristics 4
• Appropriate hormone replacement: If pituitary-hypothalamic injury is present, ensure adrenal cortical and thyroid hormone replacement therapy are also addressed 4

Key Pitfalls to Avoid

• Do not assume CDGP without proper evaluation: Delayed puberty at age 13 in boys is at the upper limit of normal (typically defined as >14 years), but complete absence of pubertal signs warrants investigation 2, 3, 6
• Monitor bone age carefully: Androgen treatment can accelerate epiphyseal closure and compromise final height if not properly managed 4
• Reassess periodically: In patients treated for presumed CDGP, regularly evaluate for spontaneous resumption of gonadotropin secretion to avoid unnecessary prolonged treatment 2
• Consider MRI if red flags present: Central nervous system symptoms (headaches, visual changes), very early onset, or abnormal hormone patterns warrant imaging of the hypothalamic-pituitary axis 1

Referral Indications

Refer to pediatric endocrinology if: Persistently abnormal hormone levels, confirmed hypogonadism, lack of progression after initial treatment, or concerns about final height and bone health 5