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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).
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
Vaccines prevent between 2.5 and 4 million deaths every year.