Difference between primary and secondary thyrotoxicosis
Answers
Answer:
Hypothyroidism is caused by a deficiency in the production of thyroid hormone and may be either primary or secondary. Primary hypothyroidism occurs when the thyroid gland does not make sufficient amounts of thyroid hormone. It is usually characterized by high levels of thyroid-stimulating hormone (TSH) and low levels of the thyroid hormones triiodothryronine (T3) and tetraiodothryonine (T4).
Secondary (or central) hypothyroidism is caused by disorders of the pituitary gland or hypothalamus. Generally, secondary hypothyroidism is associated with low TSH and low T3 and T4. However, TSH levels may also be normal or even slightly elevated. For this reason, TSH is often an unreliable measure of secondary hypothyroidism and should not be used to assess the adequacy of thyroid replacement in these patients.