How does hyperthyroidism cause brisk tendon reflexes?

The overactive thyroid releases excessive thyroxin. Thyroxin regulates how fast every cell in the body goes, including those in the nervous system. When neurons are bombarded with excess thyroxin telling them they need to go faster, reflexes quicken and the patient becomes jumpy, excitable, easily startled, and highly anxious. This is all due to the effect of thyroxin on the nervous system.




More specifically, T3 (tri-iodothyronine) is going to act intracellularly on the genes that make Sodium/Potassium ATPase pumps. T3 will also increase their activity. The process of nervous signal transduction involves depolarization of the neuron to generate an action potential. When there is increased K intracelluarly due to increased pump activity, the cell will have generated a larger membrane potential resulting in a much more reactive neuron. This will lead to hyperreflexia via hyperthyroidism. Treating the hyperthyroidism is needed to control this.