What is the recommended evaluation and treatment for a 13 year and 5 month old boy with delayed pubertal development, specifically no axillary (armpit) hair and no pubic hair, but with some testicular growth?

Evaluation and Treatment of Delayed Pubertal Development in a 13-Year-5-Month-Old Boy

This boy requires immediate hormonal evaluation with FSH, LH, and testosterone levels, bone age radiography, and referral to pediatric endocrinology if testicular volume remains <4 mL or if hormonal abnormalities are detected. 1

Initial Assessment

Key Clinical Findings to Document

• Testicular volume measurement: The presence of "some testicular growth" must be quantified—testicular volume ≥4 mL or length ≥2.5 cm indicates pubertal onset, while smaller measurements indicate delayed puberty 2, 3
• Growth velocity and height: Assess current height percentile, growth velocity over the past year, and parental heights to calculate target height 3, 4
• Family history: Document parental pubertal timing, as constitutional delay of growth and puberty (CDGP) typically shows familial patterns 2, 5
• Chronic illness screening: Evaluate for underlying conditions (gastrointestinal disease, renal disorders, respiratory illness, endocrinopathies, eating disorders) that could cause functional hypogonadism 4
• Anosmia assessment: Screen for sense of smell, as anosmia suggests Kallmann syndrome 6

Important Context About Pubic and Axillary Hair

The absence of pubic and axillary hair at this age is not necessarily abnormal if testicular growth has begun, as adrenarche (development of pubic/axillary hair) and gonadarche (testicular growth) are separate processes. Testicular development is the primary marker of male puberty 2.

Laboratory Evaluation

Required Initial Testing

• Serum FSH, LH, and testosterone (morning samples preferred): These distinguish between hypogonadotropic hypogonadism (low FSH/LH with low testosterone) and hypergonadotropic hypogonadism (elevated FSH/LH with low testosterone) 1, 2, 3
• Bone age radiography (left hand and wrist): Delayed bone age supports CDGP, while normal bone age suggests pathologic hypogonadism 2, 3, 5
• Thyroid function tests: Hypothyroidism can cause delayed puberty 2, 3
• Prolactin level: Hyperprolactinemia can suppress gonadotropin secretion 2
• Complete blood count and comprehensive metabolic panel: Screen for chronic illness 3

Additional Testing if Growth Velocity is Abnormal

• IGF-1 level: Assess growth hormone status if growth velocity is impaired 2

When to Obtain Brain MRI

Brain MRI is indicated if hypogonadotropic hypogonadism is confirmed (low FSH/LH with low testosterone) to evaluate for hypothalamic-pituitary pathology, including tumors 2, 6

Differential Diagnosis Framework

Most Likely: Constitutional Delay of Growth and Puberty (CDGP)

• Accounts for the majority of delayed puberty cases in boys 2, 5
• Characterized by: family history of late puberty, delayed bone age, normal growth velocity (though may be slow), eventual spontaneous pubertal progression 2, 5
• These patients are healthy with no underlying pathology 3

Hypogonadotropic Hypogonadism

• Congenital: Kallmann syndrome (with anosmia), isolated GnRH deficiency, genetic mutations 6
• Acquired: Pituitary/hypothalamic tumors, cranial irradiation, trauma 1, 6
• Characterized by low FSH, LH, and testosterone 2, 3

Hypergonadotropic Hypogonadism

• Causes: Klinefelter syndrome (47,XXY), testicular damage from chemotherapy/radiation, bilateral cryptorchidism with testicular failure, viral orchitis 1, 3
• Characterized by elevated FSH and LH with low testosterone 3
• Karyotype is mandatory in boys with small testes (<4 mL) and elevated gonadotropins 3

Functional Hypogonadism

• Secondary to chronic illness, malnutrition, eating disorders, excessive exercise, or endocrinopathies 5, 4
• Treatment of underlying condition typically restores pubertal progression 5, 4

Treatment Approach

For Constitutional Delay (After Excluding Pathology)

Boys aged 14 years and older may benefit from short-term testosterone therapy to initiate pubertal development 2, 5:

• Testosterone enanthate 50-100 mg IM monthly for 3-6 months is the typical regimen 7, 5
• This "jump-starts" puberty and addresses psychological distress and bone mineralization concerns 5
• Treatment should be individualized based on psychological impact and bone density 5
• Bone age monitoring every 6 months is essential during androgen treatment to assess epiphyseal maturation 7

For Confirmed Hypogonadism

• Permanent testosterone replacement therapy is required for hypogonadotropic or hypergonadotropic hypogonadism 7, 5
• Dosing starts low and gradually increases to mimic normal pubertal progression 5
• Alternative options include GnRH analogues or gonadotropins in specific cases 5

For Functional Hypogonadism

• Address the underlying chronic illness with appropriate disease-specific treatment and ensure adequate nutritional intake 5, 4
• Pubertal development typically resumes once the underlying condition is controlled 4

Referral Criteria

Refer to pediatric endocrinology in the following situations 1, 2:

• No signs of puberty by 13 years of age (this patient is at 13 years 5 months, approaching this threshold)
• Testicular volume remains <4 mL at age 14 years
• Failure of pubertal progression once started
• Abnormal hormonal results (hypogonadotropic or hypergonadotropic patterns)
• Abnormal growth velocity requiring IGF-1 assessment
• Neurologic symptoms suggesting central pathology

Critical Pitfalls to Avoid

• Do not delay evaluation beyond age 14 years in boys without clear pubertal onset, as this increases risk of psychological morbidity and bone density loss 5
• Do not assume CDGP without excluding pathologic causes, particularly in boys without family history of delayed puberty 2, 6
• Do not forget karyotype testing in boys with small testes and elevated gonadotropins, as Klinefelter syndrome is easily missed 3
• Do not overlook chronic illness as a reversible cause of delayed puberty 4
• Monitor bone age every 6 months during testosterone treatment to prevent premature epiphyseal closure 7