Central hypothyroidism

摘要

Most patients with hypothyroidism have thyroid failure or primary hypothyroidism. Central hypothyroidism (CH) is caused by impaired stimulation of a normal thyroid gland by hypothalamic or pituitary hormones. Most cases of CH are caused by pituitary tumors, but genetic defects causing abnormalities in the thyroid-stimulating hormone (TSH) < beta > subunit also lead to CH. The symptoms are similar to those of primary hypothyroidism, and most patients with CH will also have signs and symptoms of other anterior pituitary dysfunction. The diagnosis of CH can be missed if a TSH is the only screening test used for detection of thyroid disease, and we recommend measurement of both free thyroxine and TSH for screening purposes. The treatment is the same as in primary hypothyroidism except that TSH cannot be used to monitor therapy. It is important to assess the pituitary adrenal axis before starting levothyroxine to avoid precipitation of adrenal crisis in patients with adrenal insufficiency.