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How do sex hormones influence secondary sex characteristics in animals?

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Diagram comparing reproductive pathways: arrows show sexual reproduction forming a diploid zygote from oocyte and sperm, haploid parthenogenesis forming a haploid individual, and two types of diploid parthenogenesis-automixis and apomixis-both resulting in diploid individuals. Symbols indicate haploid and diploid stages. — Animal reproductive system The process of sexual reproduction and several forms of parthenogenesis.

Sex hormones, primarily androgens and estrogens, are critical in regulating the development and maintenance of secondary sex characteristics in animals. These characteristics are distinct from primary reproductive organs and are often associated with sexual drive, physical appearance, and behavior.1234

Male Characteristics

In male vertebrates, the testes secrete androgens, most notably testosterone. These hormones promote:12
* Physical Development: Androgens stimulate muscular development, skeletal growth, and, in humans, the growth of facial and body hair and the deepening of the voice.12
* Behavior: They influence male sexual behavior and aggressiveness, which are essential for competing for mates.42
* Display: In many species, androgens facilitate the development of specific features used to attract females, such as the bright plumage of birds or the antlers of a moose.4

Female Characteristics

Estrogens, produced by the ovary, maintain female reproductive tissues and stimulate the development of feminine characteristics, such as the mammary glands. In many species, these hormones also influence behaviors related to nurturing and the estrous state of preparedness for mating.24

When hormonal balances are disrupted, animals may exhibit atypical characteristics, such as the development of opposite-sex traits or suppressed sexual development.56