An underactive thyroid (hypothyroidism) occurs when the thyroid gland stops producing enough thyroid hormone, triiodothyronine (T3) and thyroxine (T4). The disease mainly affects middle-aged and elderly women, but it can also run in family groups.
The thyroid gland shrinks as its cells are destroyed by the defect in the patient’s immune system. Putting the patient on a course of thyroxine tablets is the easiest way to correct the problem.
Very rarely, defects in the patient’s immune system cause the thyroid to become enlarged (goiter), also known as Hashimoto’s thyroiditis. No treatment is necessary unless the goiter becomes so large that it looks unattractive or is compressing the trachea. If this happens, surgery to remove most of the thyroid gland and then aftercare of thyroxine tablets is recommended. In patients who are not fit enough to undergo surgery, or who do not wish to have surgery, a dose of radioactive iodine treatment may be given.
Your doctor will advise you on the best course of action, as each person is different.
Autoimmune diseases associated with underactive thyroid
Very occasionally, someone who has an autoimmune underactive thyroid has other autoimmune conditions.
•Pernicious anemia. This happens when the acid-producing cells in the stomach are destroyed and the patient cannot absorb vitamin B12. This develops into anemia (low blood count) along with nervous system symptoms.
•Addison’s disease. This is the destruction of the adrenal gland and is associated with severe fatigue and low blood pressure.
•Type 1 diabetes. This is the destruction of the insulin-producing cells of the pancreas.
• Destruction of ovaries in women and testicles in men. The results for women is the lack of menstruation and for men infertility and impotence.
•Loss of parathyroid function resulting in low blood calcium levels and the possibility of severe muscle spasms and psychological changes.
• Rheumatoid arthritis that affects the joints.
•Systemic lupus erythematosus which can cause diseases of the skin, heart, lungs,
Kidneys, joints and/or nervous system
Symptoms of an underactive thyroid
•Weight gain. You are likely to gain five to ten kilograms, although your appetite is normal or even less than usual.
• Sensitivity to cold. Feeling very cold, wanting to put on extra layers of clothing, or sit near a fire. This may be accompanied by muscle stiffness and spasms when moving suddenly.
•Mental problems. Tiredness, drowsiness and intellectual slowing, lack of concentration, poor memory and much slower reactions.
•Speech. The voice becomes slow and hoarse, sounding slurred.
•Heart. The pulse rate is slow, around 60 beats per minute. You can also have high blood pressure, the elderly are more at risk of heart failure.
• Bowel movements. Usually constipated.
•Menstruation. Periods get heavier.
•Skin and Hair. The skin is likely to be rough. Eyelids, hands and feet swell. Hair becomes dry and brittle, hair loss is sometimes experienced. The outer eyebrows seem to thin out, almost disappearing.
•Nervous system. Become a bit dead and have problems with balance.
It’s not all bad news, as after taking thyroxine tablets for a while, the symptoms go away.
Tests for an underactive thyroid
If you experience any of the symptoms described above, make an appointment with your doctor for a blood test.
A blood test measures the levels of T4, which will be low, and TSH (thyroid-stimulating hormone), which will be high.
Treatment
As mentioned above, thyroxine tablets are prescribed for an underactive thyroid.
They are available in 25mg, 50mg and 100mg doses. Typically, thyroxine treatment is started at a low dose for three to four weeks, then titrated to a higher dose for another three to four weeks. Usually after three months another blood test is done to assess whether the dose is correct. The goal is to restore T4 and TSH levels in the blood to normal.
Once on the correct dose, you will lose weight and notice that the puffiness around your eyes has disappeared. Skin and hair texture will take longer to recover, you will start to feel good again.
It is normal to continue taking thyroxine for life and that is why in the UK the prescription is ‘free’ if you have an NHS medical exemption certificate. Ask your doctor or chemist for information on this.