PURPOSE: This study aimed to assess the thickness and stiffness of the Achilles tendon in patients with primary hyperparathyroidism and compare these findings with those of healthy individuals. METHODS: Bilateral Achilles tendons of 28 patients with primary hyperparathyroidism and 28 healthy controls were evaluated using ultrasound (US) and shear wave elastography (SWE). Tendon thickness was measured with gray-scale US, while stiffness was assessed using SWE, expressed as shear wave velocity (SWV) in meters per second. US and SWE findings were statistically compared between the two groups. RESULTS: The mean Achilles tendon thickness in patients with primary hyperparathyroidism (right Achilles: 5.07 ± 0.84 mm, left Achilles: 5.16 ± 0.79 mm) did not differ significantly from that in healthy controls (right Achilles: 5.01 ± 0.50 mm, left Achilles: 4.96 ± 0.44 mm
p = 0.757 and p = 0.237 respectively). Similarly, no significant difference was observed in tendon SWV between patients (right: 8.00 ± 1.01 m/s, left: 7.85 ± 1.16 m/s) and controls (right: 7.71 ± 0.95 m/s, left: 7.36 ± 0.97 m/s
p = 0.270 and p = 0.089). Additionally, no correlation was found between serum parathyroid hormone or calcium levels and tendon stiffness (p = 0.889-p = 0.902). CONCLUSION: Primary hyperparathyroidism does not appear to influence the thickness or stiffness of the Achilles tendon when compared to healthy individuals.