DHS Science



Chapter 7 Body coordination

extra worksheet 2:

Diseases of the endocrine system

Science Understanding Verbal/Linguistic

NAME: CLASS: DATE:

It is unlikely that you think about your endocrine system as you go about your daily lives. However, it is a system that affects almost every cell, organ, and function in your body. The endocrine system regulates mood, growth and development, metabolism, and reproductive processes.

Sometimes the endocrine system does not function correctly and this causes diseases such as hyperthyroidism, hypothyroidism, Addison’s disease and Cushing’s disease.

Hyperthyroidism

Hyperthyroidism occurs when the thyroid gland (Figure 1) produces too much thyroid hormone. The prefix hyper means above. Thyroid hormone affects nearly every tissue in the body and controls the rate of metabolism. When there is too much thyroid hormone, all the functions of the body tend to speed up. The effect of this is for the person to feel nervous, anxious and irritable. They perspire more than normal, feel as though their heart is racing and experience hand tremors and muscular weakness. People with hyperthyroidism may lose weight even though they have a good appetite and eat well.

[pic]

Figure 1 The position of the thyroid gland in the neck and near the larynx.

Hypothyroidism

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone. The prefix hypo means below. The thyroid gland uses iodine to produce thyroid hormones. A lack of iodine (naturally available from seafood) in the diet may be the cause of the problem.

The symptoms of hypothyroidism are not specific, making it difficult to diagnose the condition in its early stages. The symptoms may mimic other diseases as well as some of the normal changes to the body caused by ageing. Once the disease progresses, the symptoms become more obvious. Common symptoms are fatigue, depression, some weight gain, intolerance of cold and sleepiness. Most of these are caused by a slowing of the body’s metabolism.

As the disease progresses, the heart rate slows down and the body temperature falls. These symptoms can lead to heart failure.

When hypothyroidism is diagnosed correctly, it can be treated easily with pills to replace the thyroid hormone.

Addison’s disease

Addison’s disease is a rare disease that affects men and women of all ages. It is caused by a lack of the hormone cortisol normally produced by the adrenal glands (Figure 2). The cause of the problem may be that the adrenal glands cannot produce the cortisol for some reason, or it may be that the pituitary gland does not send the necessary signal to the adrenal glands.

The symptoms of Addison’s disease may include: weakness, fatigue, weight loss and depression.

[pic]

Figure 2 The position of the adrenal glands.

Cushing’s disease

Cushing's disease is caused by the over-production of cortisol by the adrenal glands. It is a rare disease occurring in only about one in about ten thousand people. The symptoms include having an excessive amount of fat stored around the waist, insulin resistance, high blood pressure, osteoporosis, kidney stones and frequent and excessive mood swings.

Questions

1 a Identify the relationship between hypothyroidism and hyperthyroidism.

b Compare this to the relationship between Addison’s disease and Cushing’s disease.

2 Use your knowledge of metabolism to deduce why weight loss is a common symptom of hyperthyroidism.

3 Hypothyroidism was commonly diagnosed in people who lived a long way from the sea. Suggest why this relationship occurred.

4 Iodised salt is available in supermarkets and is used as table salt. This is normal salt that has iodine added to it. Propose why iodine has been added to salt.

5 Compare the symptoms of hypothyroidism and Addison’s disease.

6 Deduce why diseases of the endocrine system are difficult to diagnose.

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adrenal glands

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