In hyperthyroidism, which membrane pump is upregulated by thyroid hormones?

In hyperthyroidism, which membrane pump is upregulated by thyroid hormones?

• A. Acetylcholinesterase
• B. Adenylate cyclase
• C. Phosphofructokinase
• D. Na+/K+ ATPase

Answer: (D)

Thyroid hormones boost the expression and activity of the Na+/K+ ATPase, the sodium–potassium pump that uses ATP to move 3 Na+ out of the cell and 2 K+ into the cell. Increasing the amount and activity of this pump across many tissues raises overall cellular energy use, which contributes to the higher basal metabolic rate and heat production seen in hyperthyroidism. Maintaining ion gradients and resting membrane potential is essential, but the greater ATP demand from upregulated Na+/K+ ATPase is a key driver of the hypermetabolic state. Other options aren’t membrane pumps affected in this way. Acetylcholinesterase is an enzyme on cholinergic synapses that degrades acetylcholine, not a pump. Adenylate cyclase is a membrane enzyme that makes cAMP, not a pump. Phosphofructokinase is a cytosolic glycolytic enzyme, not a membrane pump.

Thyroid hormones boost the expression and activity of the Na+/K+ ATPase, the sodium–potassium pump that uses ATP to move 3 Na+ out of the cell and 2 K+ into the cell. Increasing the amount and activity of this pump across many tissues raises overall cellular energy use, which contributes to the higher basal metabolic rate and heat production seen in hyperthyroidism. Maintaining ion gradients and resting membrane potential is essential, but the greater ATP demand from upregulated Na+/K+ ATPase is a key driver of the hypermetabolic state.

Other options aren’t membrane pumps affected in this way. Acetylcholinesterase is an enzyme on cholinergic synapses that degrades acetylcholine, not a pump. Adenylate cyclase is a membrane enzyme that makes cAMP, not a pump. Phosphofructokinase is a cytosolic glycolytic enzyme, not a membrane pump.