1 · The slow slope · the single-cutoff trap
Testosterone falls slowly with age and varies widely between men, so a single cutoff always flags a tail of older men, which is not the same as illness.Every man past a certain age should take testosterone is the most common line in men's-health marketing. The answer in this scene: true late-onset hypogonadism (LOH) is much rarer than that line implies — but to see why, you first have to understand why so many men look low on paper.Testosterone declines on a slope, not off a cliff
· After 30, testosterone falls by roughly 1-2% a year
· It is still measurable in very old men; there is no day when it switches off
· Men of the same age differ widely: the total-testosterone reference range for healthy adult men is 264-916 ng/dL (the range the Endocrine Society 2018 guideline adopts), so the high end is several times the low end and neither man is ill
The single-cutoff trap
· The usual low T cutoff is < 300 ng/dL (labs differ slightly)
· Scan ordinary middle-aged and older men with one cutoff and the older the group, the more men fall below it — a slow slope plus wide individual variation always leaves a tail under the line
· Media and testosterone clinics call that tail a disease. The count may be arithmetically right, but it answers how many men sit below a line, not how many men are ill
Why one cutoff is not enough
· Physiological decline ≠ pathological LOH: a slow fall with age is normal ageing and does not need treatment by itself
· Symptoms ≠ low T: fatigue, lower libido and lower stamina are common in ordinary ageing and need not come from testosterone
· Morning vs afternoon: testosterone peaks in the early morning and can be 30-40% lower by afternoon and evening, so an afternoon draw often reads falsely low
· Variability: the same man can test 600 on one day and 350 ng/dL on another, so a single low value needs repeating
· Total vs free testosterone: what can enter cells and act is the free share plus the share hanging loosely on albumin — not the part gripped tightly by (last step)
Next step: shrink the apparent low T with five reversible causes.