Hours of Retention Time.  OR Treatment with hormones to replace natural hormones when the body does not make enough. For example, HRT may be given when the thyroid gland does not make enough thyroid hormone or when the pituitary gland does not make enough growth hormone. Or, it may be given to women after menopause to replace the hormones estrogen and progesterone that are no longer made by the body. Also called hormone replacement therapy.