Question

question 30 (mandatory) (1 point)
a 41 - year - old female presents to your office with irritability and restlessness that has developed over the last month. lab work reveals elevated t3/t4 thyroid hormones. which of the following would be the most helpful test to differentiate between primary and secondary hyperthyroidism?
a) free thyroxina
b) total thyroxina
c) free thyroxin index
d) thyroid stimulating hormone
e) triiodothyronine

Explanation:

Primary hyperthyroidism is due to a problem in the thyroid gland itself (e.g., Graves' disease, toxic multinodular goiter). In primary hyperthyroidism, the thyroid gland over - produces T3/T4, and through negative feedback, the pituitary gland secretes less thyroid - stimulating hormone (TSH). So, TSH is low.
Secondary hyperthyroidism is due to a problem in the pituitary gland (e.g., pituitary adenoma secreting TSH). In secondary hyperthyroidism, the pituitary gland secretes excess TSH, which in turn stimulates the thyroid gland to produce more T3/T4. So, TSH is high.
Free thyroxin, total thyroxin, free thyroxin index, and triiodothyronine levels are elevated in both primary and secondary hyperthyroidism and do not help in differentiating between the two. Only thyroid - stimulating hormone (TSH) levels can differentiate between primary (low TSH) and secondary (high TSH) hyperthyroidism.

Answer:

d) Thyroid stimulating hormone