Endocrine Abstracts

Introduction: Neutropenia can indicate infectious and hematological pathology but it can also be a sign of hyperthyroidism. For this reason, it has been suggested to perform a complete blood count before starting treatment with antithyroid drugs in case of new-onset hyperthyroidism. Antithyroid drugs can cause severe neutropenia, also called agranulocytosis, when the neutrophil count is less than 500/µl. Therefore, the use of these drugs should be reconsidered if it is less than <1000/µl, and, in the event of symptoms compatible with agranulocytosis, treatment should be interrupted according to the recommendations of the American Thyroid Association (ATA). Agranulocytosis is a rare adverse effect of antithyroid drugs, appearing in 0.1%-0.5% of cases. However, there is no evidence that neutropenia in patients with hyperthyroidism is associated with an increased risk of antithyroid-induced agranulocytes.

Objectives: We studied the prevalence of neutropenia in patients with hyperthyroidism and the variations in the neutrophil count with the use of antithyroid drugs.

Material and Methods: We analyzed 52 cases of hyperthyroidism due to Graves Basedow disease diagnosed between 2014-2020. 8 men and 44 women with a mean age of 46 years (range 22-74). We studied the presence of neutropenia at diagnosis and during treatment with antithyroid drugs (methimazole or carbimazole). We classify neutropenia as mild 1000-1600/µl, moderate 500-1000/µl and severe <500/µL.

Results: 5 patients presented neutropenia (9.61%), 2 at diagnosis and 3 during treatment. All the neutropenias found were mild (1000/µL -1600/µL), without clinical repercussions, and resolved during follow-up. Only 1 patient continued to present neutropenia from diagnosis until the 6th month of treatment. There were no cases of agranulocytosis.

Conclusions: Knowledge of the relationship between hyperthyroidism and neutropenia is essential for a correct diagnosis and treatment. Despite the limitations of our study, the cases of neutropenia in the context of hyperthyroidism were mild and the neutropenia was resolved without the development of agranulocytosis. This reinforces the idea that antithyroid treatment is not contraindicated in patients with mild neutropenia.