Thyroid disorders fall into two general categories: (1) dysfunction of thyroid hormone production; and (2) development of thyroid enlargements, called goiters which include generalized enlargement of the gland and benign and malignant nodules. Thyroid dysfunction results either from increased or decreased secretion of thyroid hormones called hyperthyroidism or hypothyroidism.
Thyroid hormones regulate the rate of metabolism, heat production, and oxygen consumption of the entire organism, as well as the concentration of specific proteins in different organs and tissues. In general, symptoms of thyroid dysfunction are related to changes in the rate of metabolism and heat production, though changes in specific proteins may also have a profound impact in the body.
In hyperthyroidism excessive concentrations of thyroid hormones circulate through the body, affecting most tissues and organs, and producing a hyper metabolic state. In this setting, patients complain of fatigue and the feeling that their body temperature is too warm. They have increased sensitivity to external heat and a rapid heartbeat (called palpitations); and they have increased and inappropriate perspiration, nervousness, excess energy, tremors, and an increased frequency of bowel movements.
In hypothyroidism serum concentrations of thyroid hormones are decreased, resulting in a hypo metabolic state. Patients complain of fatigue and sleepiness and the feeling that their body temperature is low. They have increased sensitivity to the cold and the feeling that mental function is slow. Appetite remains normal but body weight may increase modestly.
Cramping pain in the muscles and constipation are common. On examination, skin is dry and cool and the hair may be brittle. Patients have a slow heart rate, hoarse voice and slowed mental function. Swelling around the eyes occurs and the reflexes are abnormal. Such patients also have raised concentrations of cholesterol in the blood plasma and are at increased risk for heart disease.
You should see your doctor and ask to be tested for an underactive thyroid if you have symptoms including: tiredness; weight gain; depression; being sensitive to the cold; dry skin and hair and muscle aches. The only accurate way to find out if you have a thyroid problem is to have a blood test to measure your hormone levels.