The most important anti-aging hormones are HGH, DHEA, Melatonin and, to a lesser extent, Testosterone and Estrogen. These hormones together and individually give us our normal sense of well being and affect our sense of pleasure, sexual libido, help our cognitive processes such as concentration, logical thought processes, intelligence and ability to express ourselves, maintain our stamina and exercise tolerance.
So we can conclude that the aging process is associated with a decline in such qualities of life as: pleasure, libido, mental concentration and so on.
Then there are the physical attributes associated with aging: a loss of muscle mass, increase in fat deposits especially around the abdomen (so-called "middle age spread"), increase in wrinkles and loss of elasticity in the skin.
Some of the effects of this age-related "hormone deficiency" are invisible but insidious. These include an elevation of blood cholesterol and fat levels, weaker bones, weaker immune system and an increased tendency to develop heart disease and cancer.