High parathyroid hormone after thyroidectomy may be due to transient surgical injury or hyperparathyroidism. Hyperparathyroidism is categorized as primary, secondary and tertiary. Secondary hyperparathyroidism is commonly due to vitamin D deficiency, while tertiary hyperparathyroidism is commonly due to renal insufficiency. Chronic kidney disease, renal insufficiency, and reduced glomerular filtration rate increase blood phosphorus and decrease blood calcium, which stimulates parathyroid hormone secretion. Calcium salts can be given orally or the calcium content of dialysis fluid can be increased to supplement calcium deficiency and suppress parathyroid secretion. Secondary hyperparathyroidism requires treatment with calcium, active vitamin D, and possibly surgery if necessary, among other things. There are many reasons for high parathyroid hormone after thyroidectomy, and it is recommended that regular postoperative review is needed for timely and targeted treatment.