Thyroid cancer is one of the common malignant tumors of the endocrine system, accounting for 0.4% of all malignant tumors; the average incidence rate reported in foreign literature is 4/100,000 to 6/100,000. In recent years, the incidence of thyroid cancer has been on the rise, with an annual increase of 5% in the past decade. The majority of thyroid cancers are papillary thyroid cancers, and the treatment of papillary thyroid cancers is mainly surgical. There is clear evidence that taking levothyroxine tablets after thyroid cancer surgery has a good effect in preventing cancer recurrence. In the clinic, I often encounter some thyroid cancer patients who have undergone resection surgery and do not know how much levothyroxine tablets should be taken after surgery. How to take them? This is always a problem for patients. 1.How much should I take? It is generally recommended that thyroid cancer patients should start taking levothyroxine tablets 2 weeks after surgery. The initial dose is one tablet (50 micrograms) per day; if the patient is older than 65 years old, or has coronary heart disease, or is a post-menopausal woman, or has other serious diseases, the initial dose should be 1/4 to 1/2 tablet per day, or even less, with slower increments and longer adjustment times. The final dose of medication depends on the monitoring of serum thyroid stimulating hormone (TSH). Since the severity of the disease and the risk of side effects from taking levothyroxine tablets varies from patient to patient, the doctor will set different treatment goals, i.e., the range of TSH values to be achieved, taking into account the patient’s actual condition. Generally speaking, for low-risk patients (early stage) TSH is controlled at around 0.5, and for intermediate and high-risk patients (middle and late stage) TSH is controlled at around 0.1. If no tumor recurrence is seen during the treatment period, the course of treatment will be 5 years for low-risk patients and 10 years for intermediate- and high-risk patients; after that, it will be changed to normal dose, as long as the TSH is controlled within the normal range. According to this goal, patients need to continuously adjust the dose of eugenol until the target is reached. During the initial treatment, patients are advised to go to the hospital every 4 weeks or so to measure TSH, which is used to decide whether to increase or decrease the dose of levothyroxine tablets; after reaching the target, thyroid function is rechecked every 2-3 months for 1 year, every 3-6 months for 2 years, and every 6-12 months for 5 years to measure TSH to ensure that TSH is maintained in the target The TSH should be maintained in the target range. 2. How should I take it for best results? The best way to maintain a stable TSH level is to take it on an empty stomach before breakfast. If you miss a dose, you should take a double dose until the entire missed dose is made up. For example, if you missed a dose yesterday, take a double dose today and start taking it normally tomorrow; if you missed a dose the day before or yesterday, take a double dose today and tomorrow and start taking it normally the day after. And so on. In addition, certain special drugs or foods should be taken at sufficient intervals: 1 hour between vitamins and tonic products; 2 hours between foods or drugs containing iron and calcium; 4 hours between milk and soy foods; and 12 hours between lipid-lowering drugs. In this way, it is possible to ensure that a stable therapeutic level can be achieved after taking levothyroxine tablets while keeping its side effects to a minimum. For patients after thyroid cancer surgery, not only should they have the confidence to insist on taking the medication, but also the correct way to take the medication, only then can they achieve satisfactory clinical effect and reduce the possibility of cancer recurrence. Theoretically speaking, levothyroxine tablets have no adverse reactions and toxic side effects because it is a substance that the human body itself has – a substitute for hormones. Most of its toxic side effects and adverse reactions are caused by hyperthyroidism (commonly known as “hyperthyroidism”) due to long-term use of supraphysiological doses of thyroid hormone or large dose adjustments, especially TSH needs to be maintained at very low levels (<0.1mU/L) for a long time. Clinical symptoms include tachycardia, palpitations, arrhythmia, angina, headache, muscle weakness and cramps, flushing, fever, vomiting, menstrual disorders, tremors, restlessness, insomnia, excessive sweating, weight loss, and diarrhea. In these cases, the daily dose should be reduced or stopped for a few days as ordered by your doctor. Then, readjust the medication regimen. In addition, another side effect of supraphysiologic doses of thyroid hormone is an increased incidence of osteoporosis in postmenopausal women, so appropriate calcium and vitamin D supplements can be given to postmenopausal women along with levothyroxine tablet therapy.