There are numerous effects of hormones produced by the thyroid , T3 and T4 , on all the tissues of the organism. If we want to summarize the results of their action in a single concept, we can say that they keep the functions of these organs and tissues in balance. In fact, when the production of hormones by the thyroid gland increases or decreases, balance is lost and the functions respectively slow down and accelerate, at least in general.
This is why hyperthyroidism is associated with tachycardia , irritability , weight reduction and diarrhea and people with hypothyroidism can have bradycardia,fatigue , depression , weight gain and constipation .
It is important to know the mechanisms by which thyroid dysfunctions cause these and other symptoms and signs, because it helps to understand how the recovery of a correct function of the gland serves to restore the balance of the organism.
How thyroid hormones govern cell function
Thyroid hormones are not the only hormones and mediators that influence cell functioningof all tissues, but which are among those that perform the most important actions is confirmed by the fact that the receptors to which they bind are located on the membrane of the cell nucleus. This, in fact, means that the messages that they transmit to the cell arrive directly at the cell’s structure which organizes its functioning. The final effect of the binding of T3 or T4 with receptors is affected by several factors. First of all, there are various types of thyroid hormone receptors and not all receptors bind both T3 and T4. Furthermore, once the bond has been established, molecules come into play which facilitate or limit the translation of the message transmitted by the bond into a modification of the functioning of the cell, for example consuming more energy.receptor has cellular function, just think of the resistance of the tissues to thyroid hormones . When cells become “resistant” to the stimuli brought by these hormones, in the blood they detect high concentrations of T3 and T4 and normal or high concentrations of TSH . This is an anomaly because TSH should decrease as T3 and T4 increase, as occurs in hyperthyroidism . But the explanation of the anomaly lies in the fact that the resistance of the tissues to the stimuli of the thyroid hormones does not activate the feedback mechanismswhich should lead to reduced TSH secretion. Another mechanism that is part of these complex processes is the dialogue between the thyroid hormone receptors and other receptors, also located on the nucleus membrane, which regulate important functions such as the metabolic management of fats and sugars.
- Thyroid hormones have a preferential lane, inside the cell, to transmit their messages
- Several factors modulate the final effect of the messages transmitted by T3 and T4 to the cell
- These mechanisms confirm the importance of thyroid hormones in maintaining the functional balance of all organs and tissues.