Identify the possibility of hypothyroidism when the patient's symptoms include fatigue, constipation, feeling cold, impaired memory and slow heart rate.The disease is common and its symptoms may be vague. Diagnosis of hypothyroidism and treatment of hypothyroidism originating in the thyroid gland (primary hypothyroidism) are tasks of the primary health care.Hypothyroidism is easy to confirm or exclude by determining serum TSH and free T4 (FT4) concentrations.Remember that hypothyroidism can be the cause of high serum cholesterol or creatine kinase (CK) concentrations. In replacement therapy, a young or middle-aged patient usually feels best if TSH concentration is about 1–2 mU/l and FT4 concentration is close to the upper limit of the reference range.Elderly patients with e.g. angina pectoris or arrhythmias often are more susceptible to the effects of thyroxine. In them, the maintenance dose remains slightly lower and TSH concentration respectively a little higher.Ultrasonography has no role in the investigation of hypothyroidism (unless it is indicated by the findings on palpation).Thyroxine should not be used for the treatment of e.g. depression, low energy level or overweight in a person who is biochemically euthyroid.