Thyrotoxicosis and osteomalacia: from symptom to pathogenesis

Thyroid hormones have a direct effect on bone mineral homeostasis, leading to increased bone mineral resorption and calcium loss through the kidneys. Osteomalacia is conceptualized as a disorder of bone tissue characterized by inadequate or delayed mineralization of osteoid in mature cortical and spongy bone, and is associated with thyrotoxicosis. This article assessed the impact of thyrotoxicosis on the occurrence and development of osteomalacia for better diagnosis and treatment of the disease. We searched databases such as Pubmed with "osteomalacia" and "thyrotoxicosis", 15 papers were found; with "osteopenia" or "osteomalacia" or "osteoporosis" and "thyrotoxicosis", 129 papers were found. The causes of osteomalacia include insufficient intake of calcium, phosphorus and vitamin D, impaired absorption and metabolism of vitamin D, kidney diseases (nephrotic syndrome, chronic renal failure, renal tubular acidosis, Fanconi syndrome, etc.), hereditary and neoplastic hypophosphatemia, and other diseases such as heavy metal poisoning, high fluoride intake. At present, the pathogenesis of osteomalacia caused by thyrotoxicosis are mainly attributed to catabolism of vitamin D, vitamin D deficiency and mechanisms underlying calcium metabolism disorder. Since thyrotoxicosis can cause osteopenia and may coexist with osteomalacia, attention should be given to the changes of alkaline phosphatase, liver function and clinical symptoms. If necessary, chest X-ray and pelvic X-ray should be carried out to find out potential osteomalacia for timely treatment to avoid the occurrence of fracture and even deformity.