Bone fragility and osteoporosis are increasingly recognized as serious complications of endocrine disorders such as diabetes mellitus and thyroid dysfunction. Traditionally considered a disease of low bone mass, osteoporosis is now understood as a condition of compromised bone strength due to defects in both bone quantity and quality. This chapter explores the complex interplay among diabetes, thyroid diseases, and skeletal health, highlighting their shared and synergistic impact on bone metabolism. In type 1 diabetes mellitus (T1DM), early disease onset and lifelong insulin deficiency contribute to low bone mineral density (BMD) and increased fracture risk, while in type 2 diabetes mellitus (T2DM), normal or elevated BMD paradoxically coexists with poor bone quality and high fracture rates. Thyroid hormones also play a critical role in bone turnover: hyperthyroidism accelerates bone resorption, whereas hypothyroidism suppresses bone remodeling, both resulting in structurally weak bone despite differing BMD profiles. When diabetes and thyroid dysfunction co-occur, their overlapping pathophysiological mechanisms—such as altered remodeling, collagen degradation, impaired calcium homeostasis, and increased fall risk—exponentially increase fracture susceptibility. Importantly, traditional BMD assessments may underestimate true fracture risk in this population. This chapter advocates for routine screening of bone health and thyroid function in diabetic patients and vice versa, careful selection of therapeutic strategies to avoid iatrogenic skeletal damage, and implementation of lifestyle modifications and pharmacologic treatments tailored to fracture risk. A comprehensive, multidisciplinary approach is essential to reduce the burden of skeletal complications in individuals affected by these interconnected endocrine disorders.