Valuable notes on Sex Hormones for medical students

These hormones are testosterone, oestrogene and progesterone produced by the adrenal cortex of both males and females. The adrenal gland is the source of sex hormones until the testes and the ovaries mature at puberty. The secretions of these hormones are controlled by the adrenocortico-tropic hormone (ACTH) of the pituitary gland which stimulates the testes and ovaries. Their functions are:

1. To influence the development and maintenance of the secondary sex characteristics in both male and female.

2. To increase the deposition of protein in the muscles and reduce the excretion of nitrogen especially in the male.

The Adrenal Medulla

The medulla is completely surrounded by the cortex and when stimulated by the sympathetic neurons produce two hormones called adrenalin and noradrenalin. These hormones bring about the following effects on the body:

1. Dilatation of the coronary arteries, thus increasing the blood supply to the heart muscle.

2. Dilatation of the bronchi allowing a greater amount of air to enter the lungs.

3. Dilatation of the blood vessels to the muscles, increasing the supply of oxygen and nutritional material to the muscles.

4. Constriction of the blood vessels to the skin thus raising the blood pressure.

5. Increasing the rate of change of glycogen to glucose, thus ensuring sufficient glucose for sustained muscle contraction.

6. Dilatation of the pupil of the eye, due to stimulation of radiating muscle fiber of the iris.

7. Slowing down of peristalsis in the alimentary tract.

8. Reducing the secretion of saliva and other digestive juices.

9. Increasing the tone of the anal and urethral sphincter muscle, thus inhibiting micturition and defaecation.

10. Increasing the activity of the sweat glands.

Thus Adrenalin and noradrenalin prepare the body to deal with abnormal conditions so that it responds effectively to fear, excitement and danger. The islets of Langerhans Islets of langerhans are secretary cells found in clusters distributed throughout the substance of the pancreas.

They are responsible for the internal secretions insulin and glucagon. Both these hormones influence the level of glucose in the blood each balancing the effect of the other. Glucagon tends to raise the blood glucose level and insulin reduces it. Insulin is responsible for the normal metabolism of sugar in the body. Without insulin, the muscles are unable to sue the sugar circulating in the blood, which supplies them with energy.

Deficiency of insulin in the body leads to a disease called Diabetes melletus, in which the blood-sugar is high and sugar is passed in the urine.

The Pineal gland or body

The pineal gland is a small reddish grey structure, about the size of a pea situated between the under surface of the cerebrum and the mid-brain, just in front of the cerebellum. Its structure suggests the possibility that it serves some endocrine function, but there is no reliable evidence about it. It may be associated with the development of the gonads by influencing the release of gonadotrophic hormones from the anterior pituitary.

The Sex glands or Gonads

The sex glands consist of the ovaries in the female and the testes in the male. In addition to their ordinary reproductive functions, (the production of Ova by the ovaries and spermatozoa by the testis), both produce hormones which have more general effects.

1. Internal secretions of the ovary

Ovary is mainly concerned with the reproductive functions, and produce:

(a) Oestrogen which plays an important part in the regulation of menstruation and development of the secondary sex characteristics of the female.

(b) Progesterone, which prepares the uterus for the reception of the fertilized ovum.

2. Internal secretion of the testes

Testis controls the secondary sexual characteristic of the male. The hormones is called as androgens, the most important being testosterone.