13. Hyperhidrosis
Perspiration, or sweating, is a physiological process that is necessary to control body temperature during physical exertion or in harsh environments. Sweating is regulated by the sympathetic nervous system. When this system suffers from pathological alterations, it can become hyperactive and operate at a higher level causing profuse sweating in certain areas of the body at times which do not correspond with increased body temperature. This condition is known as hyperhidrosis. Hyperhidrosis can be primary, that is, of unknown cause or secondary to endocrine disorders such as thyroid diseases.