Liothyronin Sodium CAS:55-06-1

Trijodtyronin, även känd som T3, är ett sköldkörtelhormon. Det påverkar nästan alla fysiologiska processer i kroppen, inklusive tillväxt och utveckling, ämnesomsättning, kroppstemperatur, och hjärtfrekvens.

Produktion av T3 och dess prohormon tyroxin (T4) aktiveras av sköldkörtelstimulerande hormon (TSH), som frigörs från hypofysen. Denna väg regleras via en återkopplingsprocess med sluten slinga: Elevated concentrations of T3, and T4 in the blood plasma inhibit the production of TSH in the pituitary gland. As concentrations of these hormones decrease, the pituitary gland increases production of TSH, and by these processes, a feedback control system is set up to regulate the amount of thyroid hormones that are in the bloodstream.

As the true hormone, the effects of T3 on target tissues are roughly four times more potent than those of T4.Of the thyroid hormone that is produced, just about 20% is T3, whereas 80% is produced as T4. Roughly 85% of the circulating T3 is later formed in the thyroid by removal of the iodine atom from the carbon atom number five of the outer ring of T4. In any case, the concentration of T3 in the human blood plasma is about one-fortieth that of T4. This is observed in fact because of the short half-life of T3, which is only 2.5 days.This compares with the half-life of T4, which is about 6.5 days.

Liothyronine is the most potent form of thyroid hormone. Chemically, it is nearly identical to triiodothyronine (T3). As such, it acts on the body to increase the basal metabolic rate, affect protein synthesis and increase the body’s sensitivity to catecholamines (such as adrenaline) by permissiveness. The thyroid hormones are essential to proper development and differentiation of all cells of the human body. These hormones also regulate protein, fat, and carbohydrate metabolism, affecting how human cells use energetic compounds.

In comparison to levothyroxine (T4), liothyronine has a faster onset of action as well as a shorter biological half-life, vilket kan bero på mindre plasmaproteinbindning till tyroxinbindande globulin och transtyretin.

Läkare kan använda detta istället för eller utöver levotyroxin (T4) för patienter som genomgår sköldkörtelabstinenser. När en patient har sköldkörtelcancer eller Graves’ sjukdom, ablationsterapi med radioaktivt jod kan användas för att avlägsna eventuella spår av sköldkörtelvävnad. För att 131I-terapi ska vara effektiv, spåret av sköldkörtelvävnaden måste vara sugen på jod. The best method is to starve the tissue of iodine but this can lead to hypothyroid symptoms for the patient. Withdrawal from levothyroxine can be done but it takes six weeks of withdrawal for the remaining thyroid tissue to be completely starved. Six weeks is needed owing to levothyroxine’s long half life. Six weeks can be inconvenient for the patient and delay treatment. Liothyronine instead can be taken and withdrawn from for two weeks to starve the thyroid tissue. This is much safer and more convenient than levothyroxine.