Do Testosterone Tests Show Large Swings?

I’m a 72-year-old man. A blood draw on 11/4/09 at 12:33 pm showed that I had a total testosterone level of 279 ng/dL (ref. range 175-781).

On 4/1/10 at 10:26 am, I had a total testosterone level of 266 ng/dL (ref. range 280-800).

After the 4/1/10 reading, I used Androgel (1%, 3 pumps) for 1.5 years. I recently volunteered for a clinical trial of a new testosterone product and they had me stop Androgel for a 14.5-day washout period. At the end of the period, on 11/15/11, at 9:25 am, their lab reported a total testosterone level of 543 ng/dL (ref. range 300-1050).

This huge increase--over twice the previous reading--puzzles me. Are such big swings usual or not? Can Androgel jumpstart natural testosterone production, or is there a rebound affect from suddenly stopping Androgel application? Have I been miraculously cured of "low T"? Or is the reading likely erroneous?

[usarpone]

Another possibility has occurred to me: Could pathologies be involved?