Symptoms of Hashimoto's Thyroiditis: Introduction. The types and severity of symptoms of Hashimoto's disease vary between individuals. Many people have no symptoms at all. If Hasimoto's disease leads to hypothyroidism, symptoms of an underactive thyroid may develop. At the onset of hypothyroidism, symptoms can be vague and develop slowly. They may not include weakness, weight gain, cold sensitivity, cold hands and feet, fatigue, dry skin, brittle nails, and thinning, brittle hair.