Thyroid, adrenal, pancreas and the other glands

The thyroid gland lies in the neck in front of the windpipe. It has two lobes joined by a narrow bridge, the isthmus. It makes thyroxine, which the gland can only do with iodine. Thyroxine affects physical and mental growth and development, sets the basal metabolic rate, increases the absorption of simple sugars from the intestine, and helps keep skin and hair healthy. The thyroid also makes calcitonin, which lowers the calcium level of the blood and stops calcium being withdrawn from the bones. Too little thyroxine is hypothyroidism. Its common cause is a shortage of iodine in food, water and air, which makes the gland swell: simple goitre. Iodine added to salt and food prevents it. A severe lack of thyroxine causes cretinism, when it happens in childhood and slows growth and development, or myxoedema, when it happens in an adult and slows the metabolism. Too much thyroxine is hyperthyroidism, which speeds the metabolism up: in exophthalmic goitre the gland is enlarged and the eyes bulge. This is biology, not a way to check a person: a doctor decides whether anyone has a thyroid problem. The four small parathyroid glands, two on each side of the thyroid, make parathormone when the blood calcium is below normal. Parathormone and calcitonin work together to keep calcium steady. Too much parathormone lets too much calcium leave the bones and raises the blood calcium, and too little lets it fall. Either way the balance that bones, muscles and nerves depend on is upset, and a doctor decides what is wrong.