What is subclinical hyperthyroidism?
Early on in the development of hyperthyroidism, before symptoms are apparent thyroid hormone blood tests become abnormal and show the characteristic pattern of a low blood TSH level and a high normal or frankly high thyroxine level. This happens most commonly when doctors order or get the results of thyroid hormone tests during routine screening even when they do not suspect thyroid hormone over-activity.
• Subclinical hyperthyroidism is a condition where the amount of thyroid stimulating hormone (TSH) in your blood is slightly lower than normal. This hormone is produced by the brain, in the hypothalamus and the pituitary gland. The TSH controls how the thyroid gland works by telling it how much thyroid hormones to make. The thyroid gland is a butterfly-shaped organ that is located in the front part of your neck. Thyroid hormones help control body functions such as heart rate, growth, and body temperature. The thyroid hormones also control how your body uses energy, and affects weight gain and loss. • There are two forms of thyroid hormones in the blood, the T3 and T4. When these hormones become low, the brain releases more TSH to tell the thyroid to make more hormones. If the thyroid hormone levels are too high, the brain slows down making TSH. With subclinical hyperthyroidism, the TSH is slightly lower than normal while the thyroid hormone levels are normal. What causes or increases m
Subclinical hyperthyroidism is a diagnosis that has emerged as a result of the increasing sensitivity of blood tests used to measure TSH levels. When these blood tests were first introduced for use in practice, they were primarily used to detect elevated TSH levels. The original versions of these blood tests were not sensitive enough to distinguish normal TSH levels from suppressed TSH levels. With further refinement, succeeding generations of blood tests were able to provide much more sensitive measurements of TSH levels. The precision of measurement gradually increased to the point where second and third-generation blood tests could be used to distinguish normal TSH levels from suppressed TSH levels. With widespread use of second and third-generation blood tests, it became apparent that there are some patients with suppressed TSH levels who actually have normal thyroid hormone levels. Strictly speaking, these patients do not meet the criteria necessary to make a diagnosis of thyrotox
