Is axillary hair development at Tanner stage 2 normal for a 9-year-old female?

Axillary Hair Development in a 9-Year-Old Female

Axillary hair development at Tanner stage 2 in a 9-year-old female is considered premature adrenarche and warrants further evaluation, as it occurs before the expected age of 8 years in girls. 1

Understanding Premature Adrenarche

Premature adrenarche refers to the early maturation of the adrenal gland resulting in:

• Development of pubic hair before age 8 in girls
• Development of axillary hair before age 8 in girls
• Adult-type body odor
• No other signs of sexual development (such as breast development)

Clinical Significance

Premature adrenarche was once considered benign but is now recognized as potentially associated with:

• Insulin resistance (sometimes already recognizable in childhood) 2, 3
• Higher risk for developing polycystic ovary syndrome (PCOS) in adolescence 3, 4
• Potential development of metabolic syndrome later in life 5, 6

Evaluation Approach

Physical Examination

• Complete Tanner staging assessment (pubic hair, breast development)
• Assessment of growth velocity and height
• BMI calculation and plotting on growth charts
• Blood pressure measurement
• Examination for other signs of androgen excess:
  • Acne
  • Hirsutism
  • Clitoromegaly (clitoral width should be <10mm) 7

Laboratory Evaluation

For a 9-year-old female with axillary hair development, the following tests are indicated:

• DHEA-S and androstenedione levels
• Free and total testosterone
• 17-hydroxyprogesterone (to rule out non-classical congenital adrenal hyperplasia)
• LH, FSH (to assess for central precocious puberty)
• Fasting glucose and insulin levels (to assess for insulin resistance)

Imaging

• Bone age assessment via X-ray of the left hand and wrist
• If there are concerning findings on physical exam or laboratory tests, consider:
  • Pelvic ultrasound to assess ovarian and uterine size
  • Adrenal imaging if significantly elevated androgens

Management

The management approach depends on the evaluation findings:

1. If isolated premature adrenarche (normal bone age or minimally advanced, normal hormone levels):

   • Regular monitoring of growth, development, and pubertal progression
   • Annual assessment for metabolic abnormalities (fasting glucose, insulin)
   • Reassurance that this may be a normal variant

2. If evidence of insulin resistance or metabolic abnormalities:

   • Lifestyle modifications (diet, exercise)
   • Consider referral to pediatric endocrinologist for consideration of insulin-sensitizing agents 5

3. If evidence of central precocious puberty (breast development, advanced bone age, elevated LH/FSH):

   • Referral to pediatric endocrinologist for consideration of GnRH analog treatment 1

Follow-up and Monitoring

• Regular monitoring of growth velocity and pubertal progression every 6 months
• Annual screening for metabolic abnormalities
• Education about potential long-term risks and importance of healthy lifestyle

Key Points for Parents

• Axillary hair at age 9 is considered premature and warrants evaluation
• While it may be benign, it could indicate increased risk for future metabolic or hormonal issues
• Early identification allows for preventive measures and monitoring
• Regular follow-up is important to monitor for development of other pubertal changes or metabolic issues

Remember that premature adrenarche is a diagnosis of exclusion, and other causes of early androgen production must be ruled out before making this diagnosis 6.