# Non-autoimmune Familial Hyperthyroidism in Children: The Importance of Genetic Testing

## TL;DR

A 16-year-old with non-autoimmune hyperthyroidism and family history was found to have a TSHR gene variant, showing the importance of genetic testing in such cases.

## Contribution

Highlights the role of genetic testing in diagnosing non-autoimmune familial hyperthyroidism in children.

## Key findings

- A TSHR gene variant c.2009A>G p.(Asn670Ser) was identified in a patient with non-autoimmune hyperthyroidism.
- The patient's condition improved with methimazole treatment and clinical monitoring.
- The case emphasizes the need to consider genetic causes in hyperthyroidism without autoimmune markers.

## Abstract

Hyperthyroidism of non-autoimmune etiology is an uncommon occurrence, and its etiology may be the result of germline variants capable of activating the thyroid-stimulating hormone receptor (TSHR). The case of a 16-year-old adolescent with a family history of hyperthyroidism and negative antithyroid antibodies is presented. Imaging revealed bilateral subcentimeter nodules, and thyroid scintigraphy showed normal, heterogeneous uptake, with no hyperfunctioning areas. Genetic testing identified the likely pathogenic variant c.2009A>G p.(Asn670Ser) in the TSHR gene, which has been previously described in families with non-autoimmune hyperthyroidism. The patient is undergoing treatment with methimazole, with normalization of thyroid function and clinical surveillance.

This case highlights the need to consider alternative etiologies of hyperthyroidism, particularly in the absence of autoimmune markers and in the presence of a strong family history, reinforcing the role of genetic testing in this clinical context.