3. Muscular cramps
A cramp is a sudden and involuntary contraction of a group of muscular fibers. The contraction is so excessive and intense that we feel pain, and our limbs or other parts of the body that are affected by the cramp can fold inwards out of our control, thus rendering us incapable of moving them for as long as the cramp lasts. In most cases, cramps have muscular causes. Either the muscle is overstressed, or injured, or has been kept in a bad position for a long time.
There are some cases, however, where muscular cramps are caused by a hormone deficiency, namely, insufficient levels of the hormone insulin. Insulin induces cells to absorb sugar from the bloodstream, which they need so they can obtain the energy to properly function. Without enough insulin, the sugar intake is deficient, and as a consequence we could feel cramps in the muscles.