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Adolescents often feel clumsy during puberty because during this time of development, their hands and feet grow faster than their arms and legs do. The body is therefore out of proportion. One out of five adolescents actually experiences growing pains during this period.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Acetaminophen (Tylenol) in overdose can seriously damage the liver. It should never be taken by people who use alcohol heavily; it can result in severe liver damage and even a condition requiring a liver transplant.
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).
Calcitonin is a naturally occurring hormone. In women who are at least 5 years beyond menopause, it slows bone loss and increases spinal bone density.