What do Free T4 and TSH test results mean?

Question
Hello doctor,
I tested with free T4 test result of 0.555 and TSH 68.87. The doctor asked me what the Free T4 and TSH test results mean? If sick, is it serious? Currently, I am breastfeeding, can I be treated? Thank you doctor.
Hoang Thi Tam (1988)
Answer
Answered by Master, Doctor Tran Thi Huyen Trang - Laboratory Department, Vinmec Times City International Hospital
Hello,
To the question “Test results” What does the Free T4 and TSH test mean? ", the doctor would like to answer as follows:
Thyroid-stimulating hormone (TSH): It is a pituitary hormone involved in regulating thyroid hormone secretion, if thyroid hormone decreases, the pituitary gland will produce more TSH to stimulates the thyroid gland to produce more thyroid hormone. If thyroid hormone is elevated in the blood, the pituitary gland reduces its production of TSH to reduce thyroid hormone production.
T4 Is the major form of thyroid hormone in the circulating blood.
T4 exists in 2 forms:
Free T4 (FT4): accounted for 0.02% and is the biologically active form; T4 bound to protein: accounts for 99.98% and is the biologically inactive form. Interpretation of results: Elevated TSH and low FT4: Reflecting primary hypothyroidism due to thyroid disease.
Low TSH and low FT4: Reflects hypothyroidism due to a problem with the pituitary gland. Low TSH and elevated FT4: Reflecting hyperthyroidism due to thyroid disease or overdosage of thyroid hormone. Because in the results you do not specify the testing unit and the type of testing machine, you cannot accurately assess the increase/decrease of these two tests. You need to see an endocrinologist to do some more related tests to accurately diagnose the condition and find the cause of the disease to have a specific treatment plan.
If you still have questions about Free T4 and TSH test results, you can go to a hospital of Vinmec Health System for further examination and advice. Thank you for trusting and sending questions to Vinmec. Wishing you lots of health.
Best regards!