Alzheimer's disease 
Named for Dr. Alois Alzheimer, who first described the disease in 1907, Alzheimer's disease causes gradually increasing dementia, including memory loss, confusion, problems with judgment, planning and concentration, and personality changes; in its later stages it also affects physical abilities. The disease's causes, cures and preventions are unknown.

Arteriosclerosis 
The process of disease in blood vessels leading to narrowing and diminished blood flow. Atherosclerosis occurs when cholesterol and other lipids are deposited in the artery wall, and inflammation and other degenerative processes cause the vessel to become obstructed. Atherosclerosis involves primarily arteries and reduced blood flow leads to damage of the tissues that do not receive enough oxygen and nutrients. Also called hardening of the arteries.

Body mass index 
The standard measure of body fat. BMI is calculated based on an individual's weight relative to their height, and measured by multiplying the individual's weight in pounds by 703 and then dividing that number by the individual's height in inches squared.

Cholesterol 
 A soft, waxy substance manufactured by the body and used in the production of hormones, bile acid, and vitamin D. It is present in all parts of the body, including the nervous system, muscle, skin, liver, intestines, and heart. Cholesterol regulates membrane fluidity, functions as a precursor molecule in various metabolic pathways and as a constituent of low-density lipoproteins may cause arteriosclerosis.

Diabetes 
Elevations of blood sugar due to deficient insulin production or action.

Dietary supplement 
Congress defined the term dietary supplement in the Dietary Supplement Health and Education Act (DSHEA) of 1994 as a product taken by mouth that contains a dietary ingredient intended to supplement the diet. The dietary ingredients may include vitamins, minerals, herbs or other botanicals, amino acids, or dietary substances to supplement the diet by increasing the total dietary intake. Dietary supplements can be concentrates, metabolites, constituents, or extracts. They may be found in tablets, capsules, softgels, gelcaps, liquids, or powders. They can also be in other forms, such as a bar; in this case, information on the label must not represent the product as a conventional food or a sole item of a meal or diet.

Endocrine system 
Also called the hormone system, it controls the rate we grow, our feelings of hunger, our body temperature, and more.

Erectile Dysfunction (ED) 
The persistent or total inability to obtain or maintain an erection during sexual stimulation firm enough to being or complete sexual intercourse. 

Erection
The state in which the penis fills with blood and becomes rigid.

Hormones 
Chemicals that stimulate or regulate the activity of cells or organs

Hypogonadism 
A reduced or absent secretion of hormones from the sex glands (gonads). In men, these are the testes.

Impotence 
The common, less medically correct term for erectile dysfunction.

Insulin resistance 
Decreased sensitivity to the action of insulin. Typically measured as the degree that glucose is cleared from the blood in response to a given amount of insulin.

Libido
A person's sex drive

Male hormones 
Also called androgens.  They are produced in the testes and adrenal glands and are responsible for typical male sexual characteristics. Testosterone is the most well known of these hormones. The others are DHEA, dihydrotestosterone, androstenedione. (Other hormones that are not androgens, but still play a role are estrone, and progesterone.)

Multiple sclerosis 
MS is thought to be an autoimmune disease that affects the central nervous system (CNS). 

Nervous system 
This system sends the messages from the brain to the rest of the body.  It is divided into two main systems, the central nervous system (CNS) and the peripheral nervous system.

Parkinson's disease 
A slowly progressive degenerative disorder of the central nervous system characterized by slowness or poverty of movement (bradykinesia), rigidity, postural instability, and tremor primarily while at rest.

Peyronie's disease 
A condition in which a plaque, or hard lump, forms in the penis and reduces flexibility, causing pain and forcing the penis to bend or arc during erection.

Placebo effect
The measurable, observable, or felt improvement in health not attributable to treatment.  A placebo is a medication or treatment believed by the administrator of the treatment to be inert or innocuous.

Prostate
The prostate is the gland in men that manufactures fluid for semen. About the size of a walnut, it's located between a man's bladder and his rectum and surrounds the urethra (the tube that carries urine from the bladder).
Renal  Kidney related.

Testicles (testes; singular testis) 
Part of the male reproductive system. The testicles manufacture the male hormones, including testosterone, and produce sperm, the male reproductive cells. The testicles are located inside the scrotum, the loose sac of skin that hangs below the penis.

Testosterone 
The male hormone that is essential for sperm production and the development of male characteristics, including muscle mass and strength, fat distribution, bone mass, and sex drive

Vascular system
Also called the circulatory system, it is made up of the vessels that carry blood and lymph through the body.