Stress-induced increase of testosterone: contributions of social status and sympathetic reactivity.

The vast number of studies in both human and animals confirm the inhibiting role of different stressors in the hormonal function of the testicles, decreasing the testosterone (T) level in the blood. However, there also are data suggesting that stress does not invariably inhibit the activity of the testicles. Moreover, the T level in blood may be increased at initial stages of acute stress. Some researchers believe that the last phenomenon is prevalent in organisms that have (i) greater experience in winning in agonistic competitions and/or (ii) dominant status in a population hierarchy. Taking these data into consideration, we ask: what causes different patterns of hormone shifts in dominant and subordinate animals and humans? Does the concentration of luteinizing hormone (LH) determine the blood level of T? Considering that increase of T level is not invariably combined with increased LH, we suggest that the reason for the temporary increase of T concentration in the blood in the initial phase of stress, especially when the level of LH is relatively stable, is due to the increased sensitivity of testicles to LH. It is known that the sympathetic stimulation increases testicles' sensitivity to the gonadotropic hormones. It is also known that the dominants are characterized with predominantly noradrenergic response to stress. So, it seems clear why dominants respond to stress with increased blood T more frequently than others. However, the sympathetic stimulation during stress does not always induce rise of T in the blood of the dominants. We think that the factors which contribute to the transitory increase of the blood T level in the initial stage of stress are the following: absence of chronic stress; dominant status of an animal; more or less stable social relations in a population; some behavioral characteristics, particularly an ability to manage stress situation and respond adequately to frustration; emotions resulting from a winning in agonistic contest; and and noradrenergic type of stress reactivity.