Biology of Aging
The endocrine system controls the production and distribution of hormones throughout the body. Many hormones decline with advancing age. Decline in the levels of reproductive hormones (e.g., testosterone and estrogen) could contribute to loss of function in older individuals. The degree to which such decline is responsible for loss of function, and what can safely be done about it, are important research questions.
Replacing reproductive hormones, or their precursors, could be dangerous since these hormones also play a role in the development of cancers of the reproductive organs. Hormone replacement therapy for postmenopausal women is often desirable, but its desirability depends upon a number of factors, such as family history, personal history, lifestyle, and risk tolerance. Hormone replacement therapy for male reproductive hormones and for growth hormones in both genders is much more controversial. The ready availability of hormone precursors in the form of dietary supplements poses a significant public health problem. Large numbers of people are taking substances that might cause harm without an understanding of the risks.