Because of the slow lingering course of this disease, the diagnosis of hypothyroidism is generally made by chance particularly because the euthyroidism can change unobserved into manifest hypothyroidism. In old age the course of hypothyroidism may be oligosymptomatic: only adynamia and abnormal susceptibility to cold may be diagnosed. Because of the augmented oxygen requirement of tissues during therapy with thyroid hormones the medical treatment of hypothyroidism has to start - especially in old age - with a fractional part of the final dose. In old age bland struma more and more changes to nodular struma, where small autonomic areas are often developed. Conservative therapy with thyroid hormones predominates in this case. Radioiodotherapy is indicated when medical treatment has been without success and operation is contraindicated because of high risk. Cancer of the thyroid is important - with respect to differential diagnosis - especially in older patients. Cancer of the thyroid is most common in patients aged between 50-70 years, and the anaplastic carcinoma is the most frequently observed malignant growth of old age. Concerning therapy, a radical operation comes into consideration; if radical operation is combined with too high risks, remaining tissue may be treated by radioiodotherapy without danger.