A 13-year-old girl was treated for acute leukaemia ten years ago. She has not yet started menstruating and her mother is concerned about her development.

Which SINGLE clinical feature would be the FIRST indicator of normal pubertal development? 

1. Epiphyseal fusion

2. Breast bud development

3. Pubic hair development

4. Axillary sweating

5. Secondary dentition

Both chemotherapy and radiotherapy are associated with ovarian failure, which is more likely to occur when treatment is at younger age. 

Breast buds are the first sign of female puberty and absence of breast development in a girl older than 13.5 years requires endocrine assessment to ascertain the cause of the delay.