Objective: Apathetic hyperthyroidism can be misdiagnosed or diagnosed late, and older patients are often susceptible to adverse effects of treatment for thyrotoxicosis. The aim of this study was to identify factors associated with apathetic hyperthyroidism. Methods: We retrospectively examined serum calcium, phosphorus and bone-specific alkaline phosphatase (BAP) levels and thyroid-associated variables in 140 patients with apathetic hyperthyroidism, 456 patients with typical hyperthyroidism and 120 healthy subjects. Results: Significant differences were identified with respect to age, serum calcium and corrected calcium, serum phosphorus, thyroid-stimulating hormone (TSH), free triiodothyronine (FT₃), free thyroxine (FT₄), the FT₃/FT₄ ratio, alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine, BAP and albumin among the typical and apathetic hyperthyroid and normal groups (all p < 0.001). Univariate logistic regression showed that age, serum calcium and corrected calcium, serum phosphorus, TSH, FT₄, FT₃/FT₄ ratio, ALT, AST and BAP were significantly associated with apathetic hyperthyroidism, and multivariate logistic regression showed that age, corrected calcium, TSH, FT₄, FT₃/FT₄ ratio, BAP and ALT were significantly associated with apathetic hyperthyroidism. Conclusion: Greater age, increased corrected calcium levels, decreased TSH levels, increased FT₄, a decreased FT₃/FT₄ ratio, increased BAP levels and increased ALT levels may be significant factors for differentiating apathetic from typical hyperthyroidism. Coordinated assessment of these variables may aid in the accurate diagnosis and treatment of this disorder.