Triiodothyronine | Tiros (price for 1 blister, 50 pills)

Triiodothyronine, commonly called T3, is a thyroid hormone that controls how fast the body works. It affects metabolism, body temperature, heart rate, growth, and energy use.

T3 helps the body process carbs, fats, and proteins. When the body does not make enough T3, a condition known as hypothyroidism, metabolism slows down. This often leads to fat gain, low energy, slow fat loss, and sometimes hair thinning. Adding T3 helps restore normal thyroid levels and brings metabolism back to balance.

Low doses of T3 are usually enough to correct thyroid deficiency. At these levels, it supports normal metabolism but does not strongly burn fat. Some athletes use higher doses of T3 to speed up fat loss. When combined with a low-calorie diet, T3 can greatly increase fat burning. However, higher doses can also break down muscle tissue because the body uses more energy. For this reason, it is often paired with anabolic support to protect lean muscle.

Uses/Effects of T3

T3 raises the body’s base metabolic rate, meaning more calories and oxygen are used throughout the day.

It increases protein activity in the body. While it boosts protein building, high doses can cause protein breakdown to happen faster than muscle growth.

T3 also improves glucose use by increasing glycogen breakdown and glucose production. This helps fuel the body during activity.

When it comes to fat, T3 increases cholesterol breakdown and boosts fat burning by raising LDL receptor activity.

T3 affects the heart by increasing heart rate and contraction strength. This raises cardiac output and changes blood pressure patterns, which is common when thyroid levels are high.

Before using T3, blood tests for TSH, T3, and T4 are strongly advised.

A T3 cycle should not exceed 6 weeks and should never stop suddenly. Dosage must be reduced slowly, usually by 15–25 mcg every 3–4 days, to allow the thyroid to adjust safely.