Your doctor may suggest you try the combination therapy of T3/T4 medicine if T4 medicine is not controlling your symptoms. If your dose of thyroid hormone is too high, you may develop complications such as irregular heartbeats and, over time, osteoporosis. If you have heart disease, too much medicine can cause pain (angina) and irregular heartbeats. Your doctor will watch your thyroid levels using a thyroid-stimulating hormone (TSH) test.
Metric System: The metric system is an internationally agreed decimal system of measurement created in France in 1799. The International System of Units (SI), the official system of measurement in almost every country in the world, is based upon the metric system. In the metric system, each basic type of measurement (length, weight, capacity) has one basic unit of measure (meter, gram, liter).
The World Factbook - Appendix G. appendix g :: weights and measures. Note: At this time, only three countries - Burma, Liberia, and the US - have not adopted the International System of Units (SI, or metric system) as their official system of weights and measures. Although use of the metric system has been sanctioned by law in the US since 1866, it has been slow in displacing the American adaptation of the British Imperial System known as the US Customary System. The US is the only industrialized nation that does not mainly use the metric system in its commercial and standards activities, but there is increasing acceptance in science, medicine, government, and many sectors of industry.