Hormones

• Testosterone is a steroid hormone found predominantly in males - females produce about 10% the amount found in males
• The influence of T on sexual differentiation of a foetus starts in early pregnancy. The gonads (sex glands) are originally identical in both XX and XY embryos. In XY embryos, genetic info on Y chromosome (SRY gene) then causes gonads to become testes and start producing hormones by around week 8
• In the gonads do not become testes they become ovaries - do not produce a significant amount of hormones prenatally. T acts on the hypothalamus, without this, the brain develops as a female type. So testosterone is associated with masculinisation of the brain, such as development of areas linked to spatial skills
• XY foetuses consequently have higher levels of T, particularly between 8-24 weeks, hormone levels then low in both sexes until birth
• Surge in testosterone in boys after birth
• T stimulates development of male secondary sexual characteristics e.g. pubic hair. It affects internal and external genitalia, as well as the brain and behaviour e.g. testosterone linked to aggression.
• Effects of T on skin?

  hair growth and collagen growth
• Effects of T on sex organs?

  Sperm production and erectile function and prostate growth
• Effects of T on muscles?

  muscle growth, increased strength and increased endurance
• Effects of T on brain?

  increased sex drive, improved mood, confidence and memory function
• Effects of T on bone marrow?

  red blood cell production
• Effects of T on bones?

  maintenance of bone mass density
• Oestrogen is a group of steroid hormones (oestradiol, oestrone and oestriol) involved in the development and maintenance of female characteristics in the body.
• Oestrogen influences physical change e.g. the development of breasts and also has psychological and behavioural effects e.g. PMT.
• Diminishing oestrogen levels is associated with the onset of menopause
• Similar to how testosterone is thought to masculinise the brain, oestrogen plays a role in feminising the brain
• A small amount of oestrogen is produced in males