Thyroglobulin is a large glycoprotein secreted by thyroid follicular epithelial cells. Its production can be stimulated by factors such as TSH, iodine deficiency in the thyroid gland and thyroid-stimulating immunoglobulin, and is an indicator of thyroid pathology. The normal value of thyroglobulin is 5-40 μg/L, higher than 40 μg/L is high and lower than 5 μg/L is low. If thyroglobulin is low, it is usually due to a disease of the thyroid gland, which is often seen in hereditary hypothyroidism, nephrotic syndrome and severe malnutrition. However, this indicator is not very specific. If the thyroglobulin is low and other indicators are normal, it only indicates the presence of a problem, but it cannot diagnose the disease and must be combined with other auxiliary tests for diagnosis. Therefore, once a low thyroglobulin is present, a series of ancillary tests such as thyroid hormones and thyroid ultrasound are needed to further understand the cause of the lowered thyroglobulin. Generally, no special treatment is required and regular review is sufficient.