What is a potential side effect of PTU or methimazole?

Agranulocytopenia is a significant potential side effect associated with the use of PTU (propylthiouracil) and methimazole, both of which are antithyroid medications used to manage hyperthyroidism. This condition involves a dangerously low level of neutrophils, a type of white blood cell that is crucial for the immune response. Patients with agranulocytopenia are at an increased risk of infections due to diminished immune defense.

The mechanism is thought to involve an idiosyncratic reaction where the medication affects bone marrow function, leading to suppression of the granulocyte population. This side effect is particularly important to monitor for, as it can be asymptomatic but can lead to severe consequences if not identified promptly.

In contrast, the other options do not typically correlate with the adverse effects of either PTU or methimazole. Weight gain, hypotension, and hyperglycemia are not commonly recognized side effects of these medications, which underscores the importance of recognizing agranulocytopenia as a key risk when prescribing these drugs. Monitoring blood counts is critical when patients are on these medications to catch any hematological changes early.