Thyroid stimulating hormone 5.98μIU/ml is not normal and belongs to the elevated category. The normal range of thyroid stimulating hormone is 0.35-5.5μIU/ml. Due to the different testing methods and reagents, the reference indexes are different in different hospitals and need to be analyzed specifically. High thyroid stimulating hormone may be caused by primary hypothyroidism, Hashimoto’s disease with hypothyroidism, exogenous thyroid stimulating hormone secreting tumors (e.g. lungs, mammary glands), and recovery from subacute thyroiditis. In addition, ingestion of lithium metal, potassium iodide, and thyrotropin-releasing hormone can also increase thyrotropin. If you have elevated thyrotropin levels, you need to go to the hospital and receive active treatment.