Hypothyroidism and thyroid nodules do not necessarily have a causal relationship, but hypothyroidism and thyroid nodules can co-exist. Thyroid nodules are associated with radiation, genetics, and abnormal iodine intake. Hypothyroidism is associated with autoimmune thyroiditis, such as Hashimoto’s thyroiditis; thyroid-affecting medications, such as prednisone; treatment-induced hypothyroidism, such as thyroid surgery and iodine radiation therapy; and pituitary or hypothalamus disease. Therefore, there is no necessary causal relationship between hypothyroidism and thyroid nodules. However, hypothyroidism and thyroid nodules can co-exist, and patients with hypothyroidism may have a combination of thyroid nodules. Patients diagnosed with thyroid nodules combined with hypothyroidism should actively cooperate with doctors for treatment.