Previous studies have demonstrated that maternal thyroid dysfunction is associated with a number of neurodevelopmental disorders, such as attention deficit hyperactivity disorder and epilepsy. However, the association between maternal thyroid dysfunction and other health outcomes in offspring were either investigated in single study, or not examined. Although it is known that hypothyroidism is associated with increased fracture risk in adults, as well as reduced bone mass during childhood, the association between maternal hypothyroidism and bone health in offspring has not been studied previously. This project aims to evaluate the observational and causal association between maternal hypothyroidism and bone health in offspring.