Thyroid Problems: Diseases of the thyroid gland can lead to hyperthyroidism, hypothyroidism, thyroid nodules, thyroid goiters, or thyroid cancer. Causes of hypothyroidism include tissue loss, antibodies, present from birth, defects in the production of thyroid hormone production, and medications. Causes of hyperthyroidism include Grave's disease, goiter, thyroiditis, adenoma, or medications. Symptoms of both diseases range from constipation, fatigue, weight gain, cold or heat intolerance, to coma. Treatment depends upon the thyroid condition.