Abstract
<b><i>Introduction:</i></b> Mutations in the thyroid hormone receptor alpha (<i>THRA</i>) gene are a rare cause of thyroid hormone resistance, which leads to a pleomorphic phenotypic spectrum. Hormonal profiles are variable and subtle, making laboratory diagnoses challenging<b>.</b> Genetic evaluation can be a helpful tool in diagnosing these cases. <b><i>Case Presentation:</i></b> Three patients (P1, P2, and P3) from unrelated families presented to their endocrinologists with short stature and abnormalities in thyroid function results. P1 showed hypoactivity and mild thyroid-stimulating hormone (TSH) elevation. P2 presented with a mild developmental delay and a hormonal profile initially interpreted as central hypothyroidism. Patient P3 had severe symptoms, including hypotonia, developmental delay, normal TSH, hypercholesterolemia, severe hypertriglyceridemia, high amylase levels, and mild pericardial effusion. All the patients had low free thyroxine (FT4) levels, mild constipation, and short stature. The patients underwent exome sequencing analysis that identified three different heterozygous variants in the <i>THRA</i> gene (P1 and P2 had missense variants, and P3 had a stop codon variant). All patients were treated with levothyroxine replacement, improving their clinical symptoms, such as constipation, and neurological symptoms. P1 and P2 were also treated with the recombinant human growth hormone (rhGH). The improvements in growth velocity and height standard deviation scores (SDS) were remarkable. Notably, P1 had a total height gain of 2.5 SDS, reaching an adult height within the normal range. <b><i>Conclusion:</i></b> <i>THRA</i> gene defects can lead to growth disorders with different phenotypes. Children with <i>THRA</i> mutations can benefit from adequate treatment with levothyroxine and may respond well to rhGH treatment.