Thyroid function has long been implicated as a factor that influences bone function. More particularly, hyperthyroidism for example is associated with osteoporosis. Normal thyroid function has not previously been tested as a correlate of a continuous measure, namely bone ultrasound attenuation. The purpose of the research part of this work was to investigate whether a continuous correlation between thyroid function (the whole spectrum) and bone health exists, in the general population. Data from EPIC study (European Prospective Investigation into Cancer and Nutrition) were analysed. The outcomes are revealed in this book, along with a review of the literature and an explanation of the physiology and pathology of thyroid and bones and their inter-relation. The effects of abnormal thyroid states, smoking, exercise, vitamin D, and other factors on bone are hereby discussed. This book would appeal to any medical research enthusiast, as well as to people who want to make a small entry into the mysteries of two of the most complex, dynamic systems of the human body: thyroid metabolism, and bone as a living organ.