Dehydration occurs when there is a loss of water from the body. Water is a vital component of our body and is involved in various important functions like regulating body temperature, digestion, and carrying nutrients to cells. When the body loses more water than it takes in, either through excessive sweating, urination, or diarrhea, dehydration can occur.

Option 1: Vitamins are important for various bodily functions, but dehydration is specifically caused by the loss of water, not vitamins.

Option 2: Salts, also known as electrolytes, are important for maintaining the balance of fluids in the body. While loss of certain salts can contribute to dehydration, water loss is the primary cause.

Option 3: Hormones are chemical messengers in the body that regulate various physiological processes, but they do not directly cause dehydration.

Option 4: This is the correct answer. Dehydration occurs due to the loss of water from the body.