LArche

Thelarche, also called larche in some clinical contexts, is the onset of breast development and the first outward sign of puberty in most girls. It marks the activation of the hypothalamic-pituitary-gonadal axis, leading to rising estrogen production by the developing ovaries and growth of mammary tissue. The initial breast change is breast budding, typically Tanner stage 2, sometimes accompanied by nipple elevation or tenderness.

Timing varies but is commonly around ages 8 to 13, with differences influenced by genetics, geography, body mass, and health. Precocious puberty is defined by breast development before age 8, while delayed puberty refers to onset after age 13 or the absence of secondary sexual characteristics. Thelarche is usually followed by progression through puberty, including a growth spurt, development of pubic and axillary hair (adrenarche), and eventually menarche, which typically occurs about two to three years after thelarche.

Mechanism and assessment: Clinically, evaluation involves history, physical examination, and Tanner staging. In cases of discordant or rapidly progressing development, or if signs of hormonal imbalance or virilization are present, endocrinology referral may be indicated. Thelarche can occur in isolation or as part of overall gonadal maturation; in many girls it proceeds without complication.