Hypothyroidism, Subclinical Hypothyroidism and Related Diagnostic Tools

Thyroid hormones have a widespread effect on human metabolism. Their biochemical peculiarity is the need of iodine for their synthesis. Any lack of thyroid hormones is called hypothyroidism, the diagnosis of which can easily be established by testing a patient’s serum. However, many different forms of hypothyroidism can be distinguished. Some of them occur already at birth, are usually caused by genetic defects like those encountered in Pendred syndrome and are called congenital forms of hypothyroidism. Others are acquired during lifetime and are usually caused by either iodine deficiency or several different types of thyroiditis. Also, some very distinct drugs can cause hypothyroidism. Another differentiation is to distinguish primary forms and central forms of hypothyroidism. The term primary refers to a lack of thyroid hormones due to an impaired production of hormones at the thyroid gland itself, whereas in central forms hypothalamic or pituitary disturbances lead to an absence of thyroid stimulation.