sexdevelopment

Sex development refers to the biological processes by which an organism develops sexual characteristics and reproductive capacity. It includes genetic, gonadal, hormonal, and anatomical changes from early development through puberty and, in some cases, later changes influenced by hormones or medical intervention. The topic covers typical patterns as well as variations that occur in some individuals.

In human development, chromosomal sex is established at conception (commonly XX or XY). The presence of the SRY gene on the Y chromosome usually triggers the formation of testes. Testes secrete hormones such as anti-Müllerian hormone and androgens, promoting development of male internal and external genitals. In the absence of these signals, ovaries typically form, and the default pathway supports female genital development. The exact outcome depends on a balance of multiple genes and hormones directing the formation of internal ducts and external genitalia.

Puberty is a later phase of sex development driven by the hypothalamic‑pituitary‑gonadal axis. GnRH stimulates FSH and LH, leading to ovarian or testicular activity and rising sex hormone levels. Estrogen and/or testosterone drive the emergence of secondary sexual characteristics, growth spurts, and reproductive capability. The timing of puberty varies widely among individuals and populations.

Some individuals have differences of sex development (DSDs), where chromosomal, gonadal, or anatomical development diverges from typical patterns. Examples include certain chromosomal conditions (such as Turner or Klinefelter syndromes), gonadal dysgenesis, and androgen insensitivity. Management emphasizes respectful, patient‑centered care and multidisciplinary input, with attention to medical, psychosocial, and ethical considerations.