Any changes in the functioning of the thyroid gland may be gradual, and the onset of symptoms quite slow, which means that often people don’t realise for a long time that anything is different. It is important that the issue is identified and addressed, however, to avoid complications. In hyperthyroidism, these can include problems with the eyes, which can lead to vision loss, a sudden, extreme and sometimes life-threatening flare-up of symptoms called a thyroid storm, pregnancy complications, and an increased risk of heart failure, an irregular heart rate and osteoporosis. Hypothyroidism can also cause problems during pregnancy and with the heart, as well as a goitre – an abnormal swelling of the thyroid gland that causes a lump in the throat – and a life-threatening condition called myxedema coma if thyroid hormone levels drop very low.

Thyroid function tests look at levels of free T4 and free T3 – this is the amount of each hormone in a state that can be actively used by the body if needed. The test also evaluates the amount of TSH in the bloodstream. In hyperthyroidism, free T4 is usually elevated and TSH low, whereas in hypothyroidism, free T4 is usually lower and TSH higher than normal. The amount of free T3 is sometimes used as an additional test for hyperthyroidism. Thyroid antibodies may also be looked for as a way of identifying what lies behind the thyroid disorder.

Other endocrine disorders

This module has looked at two of the most common areas in which incorrect levels of hormones can cause problems, but any part of the endocrine system can go wrong and give rise to health issues. Two that you might have heard of are:

• Addison’s disease, a disorder in which the adrenal glands don’t produce enough cortisol or aldosterone. This gives rise to symptoms such as tiredness, muscle weakness, low mood, unintended weight loss and increased thirst
• Cushing’s syndrome occurs when there are increased levels of cortisol in the body, sometimes as a result of taking steroid medication for a long time. One of the main signs is weight gain, particularly around the chest and abdomen, as well as a puffy face, skin that bruises easily, fertility problems and mood swings.