09-06-2007, 09:11 PM
The correct answer is A. The various symptoms listed
in the question all result from hyperthyroidism (Graves
disease). The plasma of these patients contains antibodies
called thyroid-stimulating immunoglobulins
(TSI) that bind tightly to thyroid-stimulating hormone
(TSH) receptors. TSH receptor activation stimulates
thyroid hormone release from the thyroid gland, producing
hyperthyroidism. The high level of thyroid hormone
secretion caused by TSI in turn suppresses formation
of TSH in the anterior pituitary, thus lowering
TSH levels in the plasma.
The total amount of thyroid hormone in the plasma is
a combination of free and protein-bound hormone.
Over 99% of the thyroxine and triiodothyronine entering
the blood combines immediately with plasma proteins
and less than 1% is free. It should be clear that
increased secretion of thyroid hormone by the thyroid
gland would lead to an increase in both free thyroid
hormone and total thyroid hormone.
in the question all result from hyperthyroidism (Graves
disease). The plasma of these patients contains antibodies
called thyroid-stimulating immunoglobulins
(TSI) that bind tightly to thyroid-stimulating hormone
(TSH) receptors. TSH receptor activation stimulates
thyroid hormone release from the thyroid gland, producing
hyperthyroidism. The high level of thyroid hormone
secretion caused by TSI in turn suppresses formation
of TSH in the anterior pituitary, thus lowering
TSH levels in the plasma.
The total amount of thyroid hormone in the plasma is
a combination of free and protein-bound hormone.
Over 99% of the thyroxine and triiodothyronine entering
the blood combines immediately with plasma proteins
and less than 1% is free. It should be clear that
increased secretion of thyroid hormone by the thyroid
gland would lead to an increase in both free thyroid
hormone and total thyroid hormone.