- Norm variant:
If thyroid hormones allocates a sufficient number of T ₃ and T ₄ , the pituitary determines their concentration as normal and allocates the number of stimulating hormone TSH, which will be sufficient to maintain a stable level of thyroid hormones. This balance is normal.
If pathological processes have occurred in the body, as a result of which the thyroid gland synthesized less hormones, then the pituitary gland releases more TSH into the blood, thereby stimulating the thyroid gland in the context of hormone synthesis. In some cases, elevated levels of TSH accompanied by increased concentrations of thyroxine (T ₄ ). If this situation can be compensated for at this stage, then subclinical hypothyroidism takes place – there are no clinics, complaints and manifestations of the disease, but TSH is increased, and thyroid hormones are still normal. The normal level of T ₃ and T ₄ are supported only by the active thyroid stimulation by pituitary TSH.
At some point, the thyroid gland reserves are being depleted, and there is an increase in blood TSH and low thyroxine – T ₄ . This will be the insufficient function of the thyroid gland – hypothyroidism.
In the opposite situation, a high concentration of thyroid hormones leads to a decrease in the production of a stimulant hormone by the pituitary gland – TSH. This situation is called hypertoxicosis : TSH decreases and thyroxine increases.
Thyroid hormones during pregnancy
During pregnancy, the first important level of TSH hormone , because the determination of the concentration of thyroxine alone (which is within the normal range), can falsely come to the conclusion that with the body of a pregnant all right. And at this time of TSH can be elevated and the thyroid gland in pregnant will be working on the brink of its capacity, just to maintain a normal level of T ₃ and T ₄ .
At the same time, if the TSH level is normal, then thyroid hormones will also be within the normal range. If TSH increased or decreased, while exploring T ₄ and T ₃ .
If a pregnant woman is examined, she is given a referral for the study of TSH and thyroxine – T ₄ free. This is done in order to no longer send a woman to take tests, minimizing psychological stress before taking tests if the TSH level is outside the normal range (increased or decreased).
There are two indicators of thyroxine: free and bound. The fact is that hormones are not simply dissolved in the plasma, but are associated with carrier proteins. A large proportion of thyroxine is associated with the carrier. Less than 1% of all thyroxine is in a free state. It is the free hormone that exerts its effect. Therefore, the free fraction of thyroxine is determined.
Triiodothyronine T ₃ not routinely determined, but strictly on the testimony.
There is another indicator that is prescribed quite often – antibodies to thyroid peroxidase (AT-TPO). These are body proteins that are produced as a result of autoimmune processes, their action is directed against the thyroid gland and destroys its tissue. A high titer of antibodies should not be scary, since the process of destruction is quite long and a decrease in the function of the thyroid gland may not occur throughout life. An increased level of AT-TPO is a reason to regularly monitor TSH (once every 3 months).