Sex Hormones in Humans

Definition and Role

Sex hormones are chemicals produced by the endocrine system that control the development of sexual characteristics and reproduction in males and females.
These hormones are involved in the maturation of the reproductive system, the menstrual cycle, pregnancy, and sexual behaviour.

Male Sex Hormones

The primary male sex hormone is testosterone. It is produced primarily in the testes.
Testosterone is responsible for the development of male secondary sexual characteristics during puberty. These include: growth spurts, deepening voice, growth of facial and body hair, and muscular development.
It also plays a vital role in sperm production.

Female Sex Hormones

The primary female sex hormones are oestrogen and progesterone. They are produced primarily in the ovaries.
Oestrogen drives the development of female secondary sexual characteristics during puberty. These include: breast development, widening of the hips, and the initiation of the menstrual cycle.
Additionally, oestrogen helps regulate the menstrual cycle and prepares the uterus for possible pregnancy each month.
Progesterone, often called the “pregnancy hormone”, takes over after ovulation to maintain the thickening of the uterus lining, preparing it for the implantation of a fertilised egg.
If fertilisation doesn’t occur, progesterone levels drop, leading to the shedding of the uterus lining known as menstruation.

Hormonal Control of the Menstrual Cycle

The menstrual cycle is regulated by a series of hormones: Follicle-stimulating hormone (FSH), Luteinising hormone (LH), oestrogen, and progesterone.
At the beginning of the menstrual cycle, FSH stimulates the maturation of a follicle in the ovary. The maturing follicle releases oestrogen, which prepares the lining of the uterus for possible implantation and stops FSH production.
When oestrogen levels peak, it triggers the release of LH, which causes the mature follicle to release an egg in a process called ovulation.
Once the egg is released, the follicle changes into the corpus luteum, which secretes progesterone to maintain the thickened uterus lining.
If fertilisation doesn’t happen, the corpus luteum breaks down, reducing progesterone levels, and menstruation occurs. The cycle then starts again.

Importance of Sex Hormones Balance

An imbalance of sex hormones can lead to a range of health issues like infertility, polycystic ovary syndrome, endometriosis, and hormonal cancers.

Remember, the roles of these hormones are very complex and interrelated. Disruptions in one part of the system can have widespread effects on the others.