Why Hormone Replacement Therapy?
The question: Why hormones? Well let us first define hormones and their function. Following our definition, I will explain their usefulness as an anti-aging tool and the need for hormone replacement therapy (HRT) for better quality of life as we age chronologically.
The name hormone comes from the Greek word hormao meaning "I excite" and refers to the fact that each hormone excites or stimulates a particular part of the body known as the target gland. Some hormones have receptors on every cell in our body. Some target glands or organs have more receptors for certain hormones than others. It is estimated that our body contains between 10 to 50-trillion individual cells and that there are over 100 distinguishable (different) types of cells in the human body. All of which respond to the messages sent by hormones. Hormones act as a messenger to the cells from governing centers usually controlled by the brain. Our bodies could not function without hormones.
Hormones by definition are substances in the body, usually circulating in the blood, produced by a gland that has an effect on tissues at a different site. These substances are usually proteins or in the case of sex hormones steroid structures. In total there are more than 200 hormones or hormone-like substances that have been discovered thus far. Examples of protein hormones are pancreatic hormones such as insulin and glucagon or leptin produced by fat cells. Steroid hormones include corticoids like cortisol and aldosterone produced by the adrenal glands and androgens such as testosterone produced by the testes. There are several hormonal axes that is a linear arrangement of hormones (their appropriate glands); substances that release these hormones (stimulating hormones) and higher centers in the brain usually that control this function.
As an example of a hormonal axis let us look at the thyroid gland and its hormones. It is known as the Hypothalamic - Pituitary - Thyroid Axis. The thyroid gland located in the neck anterior to the larynx is influenced by hormones produced by two other organs. The pituitary gland located at the base of the skull produces thyroid stimulating hormone (TSH) that stimulates the thyroid gland to produce thyroid hormones that act on all cells of our body. Further up the axis is the hypothalamus, a small part of the brain above the pituitary gland. The hypothalamus produces thyrotropin-releasing hormone (TRH). TRH will cause the pituitary gland to secrete TSH. Thus this axis is named the Hypothalamic-pituitary-thyroid axis. There are negative feedback mechanisms set up where if adequate levels of thyroid hormone are produced it will reduce secretion of the stimulating or releasing hormones further up the axis. So in the case of primary hypothyroidism (where the thyroid gland is producing sub-optimal thyroxine (T4) hormone) you will see a rise in TSH due to the inhibition of the negative feedback response.
There are many hormonal axes present in our body and many have some interplay with each other. Sometimes steroid hormones interact with protein (peptide) hormones and vice-versa. This can make for a very complicated hormonal system. So when one system or axis fails it can have undesirable action on another system. Again taking the thyroid hormones; if there is a problem with the Thyroid axis it may have an effect on the sex hormones of a young women for example and cause her to become amenorrheic and lack the ability to have a normal menstrual cycle thus causing difficulty with conception and her ability to become pregnant.
A very important gland that may have grave consequences if producing abnormal hormones is the pituitary gland. The pituitary is the “big kahuna” or the master regulatory gland. It is divided up into anterior and posterior segments.
The Anterior Pituitary is responsible for producing adrenocorticotropic hormones (ACTH) which act on the adrenal glands, Thyroid stimulating hormone (TSH) mentioned earlier as having function on the thyroid. There is the luteinising hormone (LH) and follicle stimulating hormone (FSH) that work on the sexual hormone axis to produce estrogen, progesterone and testosterone among other things. We also find prolactin (PRL) which in involved in the lactation process and melanocyte stimulating hormone (MSH) which produces skin color pigmentation. There was much work on MSH recently for it role as a safe way to tan (and possibly for weight loss). Finally and for this discussion most importantly is Growth Hormone (GH) which has the important role of growth and healing on cells further down the axis. The posterior pituitary gland releases anti-diuretic hormone (ADH) which serves to conserve fluid excretion by the kidneys and oxytocin useful in uterine contractions. In anti-aging medicine there are a couple of hormone axes that are of higher importance and they are (in no particular order of importance): Growth Hormone, Thyroid hormones and sex hormones.
Illness and drugs also can interfere with hormone function. Again let us look just at the Thyroid. Obviously diseases such as Graves’ Disease and Hashimoto’s Disease effect function. But so do diabetes, stroke and pituitary disorders. Medications such as aluminum or calcium antacids, calcium supplements, iron supplements, and anti-cholesterol/bile acid sequestering drugs has a negative effect. There are also a host of herbs and foods with undesirable effects on the thyroid gland or thyroid HRT and they include: Buckwheat, Cabbage, Collard, Fenugreek, Flax,Bugleweed (Lycopus virginicus, Lycopus europaeus) and lemon balm (Melissa officinalis), Kale, Lentil, Oats, Rye, Soybean (tofu, soymilk, etc.), Kelp, & St Johns’ wort. There are many others that affect different hormone axes.
Why is HRT so important?
Do we age as a result of a drop in our “normal” hormone levels or is aging responsible for this drop in serum levels? This is a philosophical question that can be argued successfully from both sides. Practically or clinically there is one correct answer. Now to answer the question as to why Hormone Replacement Therapy is so important as we age. From an evolutionary perspective we will find our answer. Within the last 100 years medical advancements in industrialized nations has pushed the life expectancy or average life span up significantly. Conquering many the major killers such as infectious diseases and the use of life saving medical equipment such as the ventilator, the internal pacemaker or heart-lung machine has given us the ability to extend life. Transplant surgery is another example of what modern medicine continues to offer many of us another chance for longer life. In the year 1900 life expectancy in the USA was between 45 and 50 years. This has steadily increased (with the exception of 1918’s influenza epidemic) to where we are today with people living on average into the high 70’s. It is predicted that by 2025, we may reach 100 years as the average life expectancy of Americans.
Unfortunately, our organs and hormone glands have not kept up with this pace evolutionarily. There has not been the passage of enough time or generations with significant environmental stressors to allow for the evolution of “longer acting” hormone secreting organs or glands. Thus we are in a sense artificially altering our lifespan, circumventing our genetic predestination. Antagonistic pleiotropy may also play a role here, where cell senescence may be important as cancer prevention while young; it hinders us in later life by “killing” our hormone secreting cells. In fact we have all but removed the Darwinian process of “natural selection” by offering those with the “weaker genes” the opportunities to survive and procreate (this was not available to their ancestors just a thousand years ago.) This inability of our hormone secreting glands to “keep up with the pace” causes global hormone deficiencies once we pass the age of 40. When you look at most every hormonal axis there represents a similar drop in levels as we age. This is noted primarily with the thyroid, sex hormones and especially with growth hormone.
A drop in hormone level corresponds with the degenerative part of our life curve. There are four parts to the life curve for humans. The developmental part (birth to adolescence), vitality (late adolescence to the third decade of life) the degenerative years (30+ to 50’s) and the senescence or death part which occurs on average around 70. You can correlate almost any of the decline in hormone levels with this last life cycle. If you were a fatalist then you would accept this as your destiny. However, if one views aging as a “disease” which must be combated, it becomes necessary to implement HRT to correct these shortcomings. One cannot expect to maintain healthy cell function without proper hormonal input. Exercise, good nutrition and even supplements are not enough. Remember hormones are messengers which “tell” a cell what to do. Take away these messengers and the cells malfunction and the result is aging of the cells (on a cellular level) which corresponds to aging of organs on a system level.
Paramount to any age management or restorative medicine program, to slow down the effects of aging or reverse age-related diseases, would have HRT as a prominent fixture.