Interpretation

Increased levels of TSH are nearly always indicative of primary hypothyroidism. Some rare TSH secreting pituitary tumors can also cause increases in TSH levels. Such patients would display clinical signs of hypothyroidism. Primary hypothyroidism:> 4 uIU/ml

Decreased levels of TSH are found in primary hyperthyroidism (e.g. Graves disease, thyroid adenoma or nodular goiter). The TRH (Thyrotropin Releasing Hormone) stimulation test has been used in diagnosis of hyperthyroidism. Hyperthyroid patients show a subnormal response to the TRH test. In addition, large doses of glucocorticoids, somatostatin, dopamine and replacement doses of thyroid hormones reduce or totally blunt the TSH response to TRH. Hyperthyroidism:<0.01 uIU/ml

Normal or marginally elevated TSH levels are often seen with pituitary dysfunction, either due to intrinsic hypothalamic or pituitary disease; i.e., central hypothyroidism. Normal or marginally elevated basal TSH levels are often seen despite significant reductions in T4 and/or T3 levels. These inappropriate TSH values are due to a reduction in TSH bioactivity which is frequently observed in such cases. Routine TRH stimulation is advised to confirm the diagnosis in such cases.