Thinning hair and hair loss can be symptoms of many things, and some hair loss is part of normal life. The production of hormones fluctuates throughout the lives of both men and women, most notably as they age. As well as various medical issues, can cause hormone imbalance and, in turn, trigger and contribute to hair loss. Thinning hair and hair loss are common symptoms of thyroid conditions, such as hyperthyroidism, hypothyroidism, Hashimoto's disease, and Graves' disease.