Thyreotoxicosis

The questions I put up on the blog are all taken from previous pre-clinical tests (preklin) given at the Karolinska Institute in Sweden. This blog seems to have turned in to my study buddy at the moment.

Another practice exam question.


"Explain the etiology behind thyrotoxicosis. Describe the regulation of the thyroid hormones' synthesis and release. Explain why the heart speeds up in thyrotoxicosis. (6 points)"


Thyrotoxicosis can have different causes. Inflammation of the thyroid gland because of a virus or bacterial infection will give a rise in secretion of thyroid hormone, but it will not increase production. You can also get thyrotoxicosis by overdosing och thyroid medicine. Another case is auto-immune reaction as in Grave's disease. Here the body produces antibodies (TRAK i Swedish) against the Thyroid Stimulating Hormone Receptor. The antibodies will fasten on the receptor and stimulate it. That will give an increase in production and release of T3 and T4.

The release of Thyroid Stimulating Hormone (TSH) from the anterior pituitary gland is stimulated by Thyrotropin Releasing Hormone (TRH) that is secreted from the hypothalamus in response to stress, cold, excercise, adrenal activity.

The heart speeds up in response to an increased expression of beta-receptors on the heart muscle cells. T3 stimulates the recruitment of them to the cell membrane.

Thyrotoxicosis