Testosterone (T) is the primary male sex hormone. The brain signals to the pituitary glands in the body, which then signal to the testes to produce testosterone. The amount of testosterone in the blood is regulated through something known as a “feedback loop”. When levels are too high, the brain sends signals to the pituitary glands to reduce production.
Testosterone levels are impacted by a varying number of factors e.g. age - older men are more likely to have a testosterone deficiency. The side effects of a testosterone deficiency includes impaired sex drive, sperm production as well as being at an increased risk of prostate cancer. Testosterone plays an important role in the aforementioned factors along with growth in: muscle mass, bone strength, reproductive organs and body/facial hair.
Your testosterone levels can be measured through blood tests. The standard unit of measurement is nanograms per deciliter (abbreviated to ng/dL). The two main biomarkers measured are total and free testosterone. Free testosterone is the testosterone that is bioavailable in the blood. It is called ‘free’ because it is not attached to one of two proteins; albumin and sex hormone-binding globulin (SHBG).
The levels of testosterone can fluctuate (greatly) throughout the course of the day. This is important to remember when getting testosterone levels measured. Levels peak around 8am and drop off throughout the day. Levels are at their lowest around 8pm but climb throughout the night.
T levels are plummeting. We believe that the majority of men suffer from low T around the world as a result from poor lifestyle choices. The majority of health experts say that "300-1,200ng/dL" is a "normal" range for adult men. This is because the "normal" adult man lives poorly. Realistically speaking, no man between the ages of 18-30 should have T levels lower than 600 ng/dL. A study on the generational decline in T levels in men by Travison et al. (2007)1 found that the men aged 45-71 in 1987-1989 had around 501 ng/dL. A young man between 18-30 should not have lower T levels than a 45-71 year-old man. However, many do.
Lokeshwar et al. (2020)2 conducted research indicating that men between the ages of 15-39 between 1999-2000 had an average testosterone level of 605.39 ng/dL. In 2011-2012, this average was now at 424.96 ng/dL.
Testosterone levels have also declined generationally. A study by Rigshospitalet Clinic3 on 5,000 Danish men found that men in 1960 has 17% lower testosterone levels than men in 1920.
Another study by the Journal of Clinical Endocrinology and Metabolism (2007)1 found that a 65-year-old man in 2002 had testosterone levels 15% lower than a 65-year-old man in 1987.
KeepMyT is a source of information geared towards helping men of all ages become aware of the adverse effects of modern life on their T levels.
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A Population-Level Decline in Serum Testosterone Levels in American Men
Link - https://www.researchgate.net/publication/6732874_A_Population-Level_Decline_in_Serum_Testosterone_Levels_in_American_Men
Testosterone levels show steady decrease among young US men
Link - https://www.urologytimes.com/view/testosterone-levels-show-steady-decrease-among-young-us-men
Secular decline in male testosterone and sex hormone binding globulin serum levels in Danish population surveys
Link - https://pubmed.ncbi.nlm.nih.gov/17895324/