Synthol Injections Identified as Rare Cause of Hypercalcemia: Case report

The study, published in BMC Nephrology, was led by Dr. Magdalena Markowska and colleagues from the Department of Internal Diseases, Nephrology and Dialysis at the Military Institute of Medicine—National Research Institute in Warsaw, Poland. They describe a 60-year-old man who developed persistent high calcium levels decades after receiving synthol injections. Despite extensive testing to rule out more common causes of hypercalcemia, such as parathyroid disorders, malignancy, or sarcoidosis, the investigative team traced the source of excess calcium to the old injection sites. Muscle biopsy revealed calcified tissue filled with a silicone-like substance, confirming the long-term impact of synthol on calcium metabolism.

According to the authors, the patient initially presented with weakness, significant weight loss, and acute kidney injury. Laboratory results showed markedly elevated serum calcium and impaired kidney function. Standard interventions—including intravenous fluids, diuretics, steroids, and bisphosphonates—brought only temporary reductions in calcium levels. Imaging studies revealed calcifications in multiple organs, and high-resolution chest scans showed unusual changes in the pectoral muscles. A detailed medical history uncovered that the patient had received intramuscular injections, likely containing synthol, more than thirty years earlier to enhance muscle appearance.

Synthol is composed of approximately 85 percent oil, 7.5 percent lidocaine, and 7.5 percent alcohol. While it is known to cause local complications such as pain, muscle deformities, chronic wounds, and fibrosis soon after injection, delayed systemic effects like hypercalcemia have rarely been documented. Only a handful of similar cases have been reported worldwide. The researchers note that the mechanism is thought to resemble the body’s reaction to free silicone or paraffin oil, in which chronic inflammation and granuloma formation lead to dysregulated vitamin D metabolism and excess calcium release into the bloodstream.

The team emphasized that the patient’s hypercalcemia persisted despite aggressive medical management and recurred after initial improvement. This clinical course supports the conclusion that surgical excision of the affected muscle tissue is the most effective treatment when hypercalcemia arises from synthol deposits.

Dr. Markowska and her colleagues caution that hypercalcemia, if left untreated, can damage multiple organ systems and become life-threatening. They advise clinicians to consider a history of cosmetic or bodybuilding injections when faced with unexplained high calcium levels, even if the injections occurred many years earlier. Prompt recognition of this unusual cause is essential to avoid delays in appropriate treatment and to prevent serious complications.

The authors call for greater awareness of the long-term risks of synthol use, noting that what might initially appear to be a cosmetic procedure can have serious and lasting consequences for metabolic and kidney health.

Reference:

Markowska, M., Romejko, K., Moszyńska, Z. et al. Intramuscular synthol injections cause hypercalcemia in long-term observation: a case report study. BMC Nephrol 26, 476 (2025). https://doi.org/10.1186/s12882-025-04397-5