Abstract
Introduction: Perfluoroalkyl substances (PFAS) like Perflouroctanoate (PFOA) and Perflurooctane sulfonate (PFOS) are ubiquitous environmental contaminants that have been in industrial use for many years. Many known adverse effects include malignancies, reproductive and thyroid dysfunction. However, there is limited literature regarding PFAS causing low bone density. We report a case of a premenopausal woman with a history of exposure to PFAS who was recently diagnosed with osteoporosis.
Clinical Case: A 36-year-old lady with a history of hypothyroidism, on levothyroxine, presented to the orthopedics clinic with complaints of sudden onset right foot pain with no trauma. She was found to have a fracture of her right second metatarsal bone. Notably, over a period of five years she had suffered multiple fractures including metatarsal, elbow and a wrist fracture, all with minimal or no trauma. She denied smoking, alcohol, chronic steroid or PPI use, history of malabsorption, celiac disease, kidney stones, malignancy or liver problems. Her menstrual cycles were regular; she was on oral contraceptives in the past for dysmenorrhea. She is on Vitamin D supplementation and consumes adequate dairy products daily. There is no family history of hip fracture or osteoporosis. Labs showed: Calcium 8.9mg/dl, Phosphorus 2.4mg/dl (2.5–4.5mg/dl), intact PTH was 92.7pg/ml (8-97pg/ml), 24-hour urine calcium was undetectable. Vitamin D was 56.6ng/ml (30-100ng/ml). CBC, TSH, FSH, liver & kidney functions were all normal. Anti-endomysial, anti-gliadin and anti-tissue trans glutaminase antibodies were all unremarkable. IgA level was 362mg/dl (8–352 mg/dl). DXA scan revealed the lowest Z-score (-3.1) in the lumbar spine. She reported a history of exposure to PFAS with a blood level of 22.3ng/ml for PFOA and 48.4ng/ml for PFOS in the year 2005. Plan is to initiate bisphosphonate therapy for the treatment of osteoporosis.
Discussion: PFAS are known endocrine disruptive agents that have been used widely in making a wide range of consumer products including nonstick and stain-resistant coatings of cookware, food containers. Recent studies suggest that serum PFAS concentrations were associated with lower bone density. There was a higher incidence of lower lumbar spine bone density in patients exposed to PFOS. PFOA is believed to compete with calcitriol at the same binding site on Vitamin D receptor resulting in changes in the osteoblasts thereby decreasing bone mineralization.
Conclusion: There needs to be increased awareness about the association of low bone density in patients exposed to PFAS. This is especially important in the evaluation of premenopausal osteoporosis.
References: 1. Environ Health Perspect. 2016 Jan;124 (1):81–7, 2. J Clin Endocrinol Metab 2014; 99(6) 2173–2180, 3. Sci Rep 2020 Oct 8;1091):16789
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