The heavy drinkers are often dehydrated due to :
hyposecretion of ADH
Alcohol inhibits the secretion of Anti Diuretic Hormone (ADH). ADH is responsible for the resorption of water and electrolytes by the distal tubules and thereby reduces loss of water through urine (diuresis). Hence hyposecretion of ADH results in the urinary loss of water and dehydration.