Most endocrine glands continue to function and secrete hormones throughout an individual’s lifetime. The most noticeable change in hormonal output is in the reproductive hormones. The ovaries decrease in size and no longer respond to FSH and LH, resulting in a decrease in the output of estrogens. Although the hormonal levels of other hormones may not change with aging and remain within normal limits, some endocrine tissues become less sensitive to stimulation. For example, elderly people may not produce as much insulin after a carbohydrate-rich meal is eaten. It has been suggested that the decrease in function of the immune system is a result of the reduced size of the thymus gland.