A complex cycle
On the opposite side of the coin from yesterday's post about the effects of estrogen levels, testosterone levels also have distinct effects multiple functions. Interestingly, while Bhasin et al. (2001) found many physical performance changes related to testosterone levels in healthy young men, they did not find changes in sexual function, visual-spatial cognition, or mood. This is in contrast to Gray et al.'s 2005 study which did show dose-dependent changes in these factors for older men. These studies focus more on exogenous testosterone treatment, unlike studies of menstrual cycles, because the variations in testosterone levels seem more complex and less predictable. There seem to be several cycles which affect endogenous testosterone levels in males.
Reinberg and Lagoguey (1978) found peaks in plasma testosterone in the early morning and late evening, with a minor peak in the afternoon, although Plymate et al (1989) found that aging may blunt this peaking effect. Doering et al's 1975 study found a 20-22 day cycle in testosterone levels in 12 out of 20 volunteers. Smals et al. (1976) found that there were seasonal changes in testosterone levels as well, with levels peaking in the summer and autumn, and at their lowest in the winter and early spring. This is in addition to the normal reduction in bioavailable testosterone that Morley et al (1997) correlated with aging.
My own testosterone levels are highly predictable, because more than 90% of my serum testosterone at any given time is artificially raised. Once a week, I inject 50mg of testosterone cypionate into my thigh muscle. This seems to be the dose that works best for me, although many female-to-male transsexuals (ftms) are on different doses. It is quite common for ftms to be treated on a 2-week cycle, while other ftms use a daily, topical treatment, which give them a much more stable testosterone level. I prefer injections for convenience and cost, but found that I couldn't handle the peaks and valleys. When my testosterone levels are low, I feel moody and lethargic. When they are high, I feel invulnerable. I notice the mood variations a lot less now than when I first began testosterone therapy; I have a couple of theories as why this might be, but no way of testing them. My suspicion is that I had to build up to a baseline with my small weekly doses, and that my valleys are not as deep as they were when I was first starting. However, I think it is more likely that I've simply become used to the shifts, and have found other ways to compensate.
Reinberg and Lagoguey (1978) found peaks in plasma testosterone in the early morning and late evening, with a minor peak in the afternoon, although Plymate et al (1989) found that aging may blunt this peaking effect. Doering et al's 1975 study found a 20-22 day cycle in testosterone levels in 12 out of 20 volunteers. Smals et al. (1976) found that there were seasonal changes in testosterone levels as well, with levels peaking in the summer and autumn, and at their lowest in the winter and early spring. This is in addition to the normal reduction in bioavailable testosterone that Morley et al (1997) correlated with aging.
My own testosterone levels are highly predictable, because more than 90% of my serum testosterone at any given time is artificially raised. Once a week, I inject 50mg of testosterone cypionate into my thigh muscle. This seems to be the dose that works best for me, although many female-to-male transsexuals (ftms) are on different doses. It is quite common for ftms to be treated on a 2-week cycle, while other ftms use a daily, topical treatment, which give them a much more stable testosterone level. I prefer injections for convenience and cost, but found that I couldn't handle the peaks and valleys. When my testosterone levels are low, I feel moody and lethargic. When they are high, I feel invulnerable. I notice the mood variations a lot less now than when I first began testosterone therapy; I have a couple of theories as why this might be, but no way of testing them. My suspicion is that I had to build up to a baseline with my small weekly doses, and that my valleys are not as deep as they were when I was first starting. However, I think it is more likely that I've simply become used to the shifts, and have found other ways to compensate.