Thyroxine

It is produced by the thyroid gland found at the neck region.

It is a compound of Iodine.

Functions

1. Regulate the rate of metabolism.

This is by increasing glucose oxidation.

2. Control growth

It enhances the effect of growth hormone (somatotropin). This ensures normal growth and mental development.

3. Enhance involuntary activities (in conjunction with adrenaline) like; increased circulatory rates.

Effects of Under-secretion of Thyroxine (Hypothyroidism)

Hypothyroidism leads to under-production of thyroxin. This is caused by deficiency of iodine in the diet. Iodine is required for the formation required of thyroxine. The thyroid glands hence enlarges in attempt to produce enough thyroxine leading to goitre. Hypothyroidism leads to cretinism in children and myxoedema in adults.

Cretin children have;

• Deformed legs.
• Dry leathery skin
• Large tongue
• General body sluggishness.

Such children have poor mental development resulting in low intelligence.

Myxoedema in adults is shown by the swelling of the thyroid gland called goitre. This is due to overworking of the thyroid gland in an attempt to synthesis enough thyroxine.

Effects of under-secretion of thyroxine are;

• Low metabolic rate hence low body temperature.
• Reduced heartbeat and breathing rate.
• General body sluggishness (physically and mentally).

The low physical activity results into weight gain (obesity), retention of excess fluid (oedema) hence swollen feet and puffy face.

Control of hypothyroidism

• Use of balanced diet supplemented by iodised table salt.
• Administration of iodine tablets.

Effect of Over-secretion of Thyroxine (Hyperthyroidism)

Hypothyroidism leads to over-production of thyroxine which is due to enlargement of the thyroid gland. The swelling of the gland is known as goitre.

Effects of hyperthyroidism;

• Increased metabolism with production of much temperature.
• Increased heart rate and ventilation rate.
• In extreme cases heart failure may result a condition called thyrotoxicosis.

Control of hyperthyroidism;

• Surgery

Adrenaline

Adrenaline is produced in the medulla of the adrenal gland. Adrenaline increases metabolism to prepare the body for emergency – fight or flight response. Production of adrenaline is stimulated by sympathetic nervous system.

Effects of adrenaline

• Increased rate and force of heart beat.
• Increased blood sugar through conversion of glycogen to glucose in the liver.
• Conversion of fats to fatty acids.
• Increased rate and depth of ventilation or breathing.
• Contraction of capillaries supplying the gut and skin to divert blood to muscles.
• Dilation of capillaries supplying the heart and muscles where more oxygen and glucose is required.
• Contraction and relaxation of muscles to bring about movement.
• The overall effect is an increase in the rate of respiration in cells of the heart and muscles hence production of more energy and increase in heart rate and output.

Over-secretion of Adrenaline

This is brought about by the growth of tumour in the medulla of the adrenal glands.

Symptoms

• High blood pressure.
• Severe headache.
• Racing heart.
• Sweating
• Faintness

The resultant effect is aging of major body organs such as kidney, heart and liver.