Men’s Health and Reproductive Effort: New Directions
We argue that male-biased sex disparities in health are often grounded in life history trade-offs between maintenance and reproductive effort, with hormones acting as a pivotal agent underlying the onset of illness and disease (Bribiescas and Ellison 2007). Moreover, the broad range of human male reproductive strategies compared to those in the other great apes has the potential to allow for a greater degree of phenotypic and behavioral plasticity that can support well-being and somatic health in modern humans. This argument suggests that clinicians and public health professionals need to rethink the notion of health and illness. For example, in women, having more children has been shown to lead to significantly shorter postmenopausal life spans in some studies (Jasienska et al. 2006; Helle et al. 2002). But does this mean that childbearing should be considered an illness or health hazard? While pregnancy and lactation are not considered to be illnesses, there are life history ramifications that can have a direct bearing on women’s somatic health and well-being (Jasienska 2013). Similarly, in men, hormone fluctuations in association with reproductive state (i.e., sexual maturity and fatherhood) have the potential of contributing to variation in men’s health.
Biological anthropologists have employed between-population comparisons as a research strategy with great success. However, other opportunities are emerging that may augment our understanding of the interaction between male reproductive states, neuroendocrinology, phenotypic and behavioral plasticity, and morbidity and mortality. One such opportunity arises from recent increases in use of physician- administered testosterone supplementation. While hypogonadism, aging, fertility issues, and other factors may confound our understanding of the effects of testosterone supplementation on male reproductive strategies, the vast majority of men engaging in testosterone supplementation do not exhibit any symptoms of androgen deficiency (Araujo et al. 2007). It should be noted that some men receive prescribed exogenous androgen treatment by medical practitioners, others are not. However both practices are growing. The ethics and efficacy of this prescription practice are debatable and merit its own conversation. However, the downstream effects of testosterone supplementation on these men may provide a lens into the interaction of hormone-driven reproductive effort and health costs.
It can be hypothesized that testosterone supplementation may increase the probability of (1) mate-seeking behavior, (2) increased risky behavior, (3) decreased investment in offspring, or (4) decreased investment in pair-bonding. Concurrently, since testosterone is an anabolic steroid, testosterone supplementation also holds the potential to increase metabolic costs, potentially diverting resources away from immuno- competence, and perhaps overtaxing organ function that has already been degraded by aging (Muehlenbein and Bribiescas 2005). For example, men over the age of 65
were more likely to suffer cardiac infarctions within 90 days of initiating testosterone supplementation compared to control men (Finkle et al. 2014). It should be remembered, however, that most men taking testosterone supplements are from populations that already exhibit the highest and broadest ranges of testosterone levels, so conclusions should be tempered with caution (Ellison et al. 2002; Harman et al. 2001).
Investigators must also begin to move beyond measurements of mean plasma hormone levels when possible. Common sources of variation such as diurnal fluctuations are well known. However, hormones also often exhibit significant within-individual variation due to hypothalamic pulses of GnRH, CRF, receptor levels, and other regulatory agents. Researchers have hypothesized that steroid hormone production involves nonrandom pulsatile patterns that may generate an analogue-like signal that contributes to target receptor and tissue function (Thompson and Kaiser in press).
