Another sign of Graves' disease is hyperthyroidism, i.e., overproduction of the thyroid hormones T3 and T4. Normal thyroid levels are also seen, and occasionally also hypothyroidism, which may assist in causing goitre (though it is not the cause of the Graves' disease).
Without this greenhouse effect, the average surface temperature would be 255 degrees kelvin (-18 degrees Celsius or 0 degrees Fahrenheit); a temperature so low that all water on Earth would freeze, the oceans would turn into ice and life, as we know it, would not exist.
The pressure at the planet's surface is about 92 times that at Earth's sea level. The carbon dioxide atmosphere and thick clouds of sulfur dioxide create the strongest greenhouse effect in the solar system, producing surface temperatures of up to 460 Â°C (860 Â°F) across practically the entire planet.