Thyroid Analysis

T3, free T3, reverse T3, total T4, free T4, TSH, TSH anti-receptor antibodies (TSI)

It is necessary to go with an empty stomach for the extraction of blood. No previous appointment is necessary, the extractions are made from 8:00h – 10:30h from Monday to Friday.

The use of certain drugs that can influence the determination of hormone levels, such as amiodarone, or some corticoids such as prednisone, iodides, dopamine or lithium, must be temporarily suspended.

The results are delivered within 48-72 hours.

The thyroid is a small gland located in the neck. Its function is to secrete thyroid hormones that have very important effects on the regulation of our metabolism. The functioning of the thyroid is regulated by multiple factors and the maladjustment of one of them can easily lead to a thyroid dysfunction. Thyroid hormones participate in the metabolism of carbohydrates, lipids and increase protein synthesis.

An alteration in this gland can lead to pathologies such as hyperthyroidism (increased secretion of thyroid hormones), hypothyroidism (decreased secretion of thyroid hormones), Hashimoto’s thyroiditis…

A study of the following hormones is performed:

  • T3 or triiodothyronine. Their evaluation is more imprecise than that of free T4. As there is a transformation from T4 to T3, both in the thyroid and in the tissues, the balances between both hormones are very dynamic. As in the case of free T4, elevated levels can determine hyperthyroidism and decreased values, hypothyroidism.
  • Free T3. The less abundant form, which circulates freely in the bloodstream, without being attached to proteins.
  • Reverse T3. When the conversion of T4 is not being done properly to T3 and produces reverse T3 even though the thyroid profile is “perfect”, the person remains hypothyroid, because the hormone that regulates metabolism is deficient or cannot perform its functions properly.
  • Total T4. This indicates the total amount of thyroxine in the blood, which includes the amount attached to the proteins in the blood that help transport the hormone through the bloodstream.
  • Free T4, free tetra-iodothyronine, or free thyroxine. It is a thyroid hormone not attached to proteins. It allows the thyroid function to be analysed more accurately than the assessment of total T4, as it is the one that is really functional. High values indicate hyperthyroidism and, conversely, low levels indicate hypothyroidism.
  • TSH or thyroid stimulating hormone, serum. Produced in the adenohypophysis, it is the best way to study thyroid dysfunctions. If the values are normal, it allows ruling out both hyperthyroidism, except in very specific cases such as pituitary adenoma which produces TSH and hypothyroidism. Its levels even serve to detect thyroid alterations when the values of the hormones T3 and T4, which are also studied in this analysis, are normal.
  • TSH anti-receptor antibodies (TSI). TSIs are antibodies that order the thyroid gland to become more active and release excessive amounts of thyroid hormone into the blood. A TSH anti-receptor (TSI) antibody test measures the amount of non-stimulating immunoglobulin in the blood.

An analysis of these hormones allows to know their concentration and to be able to act in time in case of imbalance.