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Main article: SRY signaling cascade
- The SRY gene on the Y chromosome acts binds to the TESCO promoter sequence on DNA, causing SOX9 to be produced, but shuts down 3 days later.
- SOX9 continues to promote at TESCO, which leads the transcription of more SOX9 and a protein called DMRT1.
- DMRT1 also upgregulates at TESCO, but in addition blocks the transcription of FOXL2, which is part of the female gene regulatory network.
- Gonadal cells differentiate into Leydig and Sertoli cells due to the action of SOX9. Additional hormones such as Anti-Mũllerian Hormone, Testosterone/DHT etc. are released, and the tissue organizes into the male testis.
Main article: Hypothalamic-pituitary-gonadal axis
- The HPG axis becomes active at the start of puberty when a cluster of GnRH-producing neurons finishes its slow migration to the hypothalamus.
- GnRH pulses released by these neurons stimulates the production of FSH and LH (gonadotropins) in the pituitary gland.
- FSH and LH stimulate the production of testosterone in the testes.
- Testosterone inhibits the production of FSH and LH in the pituitary gland, to prevent too much circulating testosterone.
- Masculinization occurs as testosterone binds to the androgen receptor in many different tissues.
Masculinization from the Androgen Receptor
- Vocal fold tissue lengthens, and the larynx protrudes to cause an "adam's apple".
- Sebum production increases in skin cells, causing acne.
- Bone Morphogenic Protein is activated in osteoblasts, causing skeletal structure to masculinize.
- Androgenic body hair goes from vellum hair to pigmented, thicker terminal hair as the hHa7 keratin gene is activated (facial hair growth).
- Growth Hormone and IGF-1 are stimulated, causing the Epiphyseal plate to form later than in feminine development.
- Enlargement of penis and scrotal sack.
- Many other things