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Hyperthyroidism leads to an increased rate of metabolism and affects about 1% of women but only 0.1% of men. For most people, this increased metabolic rate causes the thyroid gland to become enlarged (known as a goiter).
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
Asthma cases in Americans are about 75% higher today than they were in 1980.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.