A rare presentation of hypothyroid myopathy: pseudohypertrophy of calf muscles

Pseudohypertrophy of muscles is a rare and under-recognised form of hypothyroid myopathy primarily affecting the calf muscles, in association with elevated muscle enzymes. We report the case of an adult male in his late 20s presenting with progressive bilateral calf swelling, muscle stiffness and difficulty rising from a squatting position. Despite the absence of classical hypothyroid symptoms, clinical evaluation revealed delayed reflexes and ichthyotic skin. Biochemical studies confirmed severe hypothyroidism with markedly elevated creatine phosphokinase and lactate dehydrogenase levels. MRI findings were consistent with pseudohypertrophy and muscle oedema. Initiation of levothyroxine therapy (100 μg daily) led to significant clinical and biochemical improvement over 8 weeks, including reduction in calf girth and normalisation of enzyme levels. This case underscores the importance of recognising pseudohypertrophy of muscles secondary to hypothyroidism in patients with unexplained muscle hypertrophy, as prompt thyroid hormone replacement can reverse both symptoms and underlying pathology.