The term 'thelarche' refers to what physical change?

• A. Pubic hair development
• B. Breast development
• C. Menstruation
• D. Height increase

Answer: (B)

Breast development is the term for the first noticeable physical change signaling puberty in girls, called thelarche. It happens when estrogen from the ovaries promotes breast bud formation and growth, making the chest begin to develop as a secondary sexual characteristic. This is typically the earliest visible sign of puberty, occurring before the rapid height increase and before menstruation. The other events happen at different points in puberty: pubic hair development occurs later and is driven by androgens; menstruation begins after thelarche, as the reproductive system matures; and height increase is part of the growth spurt driven by overall pubertal hormones but not thelarche itself.