It is a hormone produced in the thyroid gland, which determines the basal metabolic rate and is directly related to the weight loss-gain.
It has a lipolytic ability, but also muscle catabolism as an adverse effect.
Its administration should not exceed three weeks and that is because the Hypothalamic-Pituitary-Thyroid (HPT) axis gets easily disturbed and after a certain point the situation is irreversible.
It is required to get the lowest dose (25mg) the first week, the double (50mg) the next one and the final week tapering to 25mcg again.
Its abuse results in irregular heartbeat-tachycardia, insomnia, sweating, exophthalmos (eyes bulging), restlessness, muscle catabolism and regain of weight, as soon as someone stop its use.
It’s a typical rebound effect, since Basal Metabolic Rate (BMR) drops.
For proper gland’s health, it is advised to consume iodized salt, or even iodine in the form of kelp, along with the amino acid L-tyrosine, which is involved in biosynthesis of T3 (triiodothyronine).
T3 is more potent than T4 (thyroxine), having a shorter half-life.
Considering that T4 makes T3, when we use thyroid hormones, if we do not grant T4 – but only T3 – progressively its stocks will get decreased.
Therefore, it is better to use T4, with which T3 will be formed as well.
Of course, its combination is even stronger, but poses risks for the myocardium and muscle catabolism with prolonged overdose and without progressive reduction (for proper balance of the thyroid hormone TSH).
The axis of the thyroid hormone is very sensitive and the TSH should be set in the middle of the normal range values.
Hypo/hyper thyroidism are an outcome of various different evaluations (TSH, T4, FT4, T3, FT3, ANTI-TPO, ANTI-TG).
Athletes have ended up being hypothyroid, due to the extensive abuse of T3.