A rare presentation of hypothyroid myopathy: pseudohypertrophy of calf muscles.

An adult male in his late 20s presented with progressive bilateral calf swelling, muscle stiffness, and difficulty rising from a squatting position without classical hypothyroid symptoms.

• The patient lacked classical hypothyroid symptoms such as cold intolerance, weight gain, or fatigue at initial presentation.
• Clinical evaluation revealed delayed reflexes and ichthyotic skin as notable findings.
• The presentation was bilateral, affecting calf muscles specifically.

Biochemical studies confirmed severe hypothyroidism with markedly elevated muscle enzyme levels.

• Creatine phosphokinase (CPK) levels were markedly elevated.
• Lactate dehydrogenase (LDH) levels were also markedly elevated.
• Severe hypothyroidism was confirmed on biochemical testing despite absence of classical symptoms.

MRI findings were consistent with pseudohypertrophy and muscle oedema of the calf muscles.

• MRI was used to characterize the nature of calf muscle enlargement.
• Findings confirmed pseudohypertrophy rather than true muscle hypertrophy.
• Muscle oedema was identified as a component of the imaging findings.

Levothyroxine therapy at 100 µg daily led to significant clinical and biochemical improvement over 8 weeks.

• The levothyroxine dose was 100 µg daily.
• Treatment duration resulting in significant improvement was 8 weeks.
• Improvements included reduction in calf girth and normalisation of enzyme levels.
• Both clinical symptoms and underlying pathology showed reversal with thyroid hormone replacement.

Pseudohypertrophy of muscles is a rare and under-recognised form of hypothyroid myopathy primarily affecting the calf muscles.

• The condition is associated with elevated muscle enzymes including CPK and LDH.
• Prompt thyroid hormone replacement can reverse both symptoms and underlying pathology.
• The case underscores the importance of considering hypothyroidism in patients with unexplained muscle hypertrophy.