Romantic relationships:

Falling in love decreases men's testosterone levels while increasing women's testosterone levels. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.

However, it is suggested that after the "honeymoon phase" ends—about four years into a relationship—this change in testosterone levels is no longer apparent.

Men who produce less testosterone are more likely to be in a relationship or married, and men who produce more testosterone are more likely to divorce; however, causality cannot be determined in this correlation.

Marriage or commitment could cause a decrease in testosterone levels.

Single men who have not had relationship experience have lower testosterone levels than single men with experience.

It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.

Married men who engage in bond-maintenance activities such as spending the day with their spouse and/or child have no different testosterone levels compared to times when they do not engage in such activities.

Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities are more relevant to changes in testosterone levels.

Men who produce more testosterone are more likely to engage in extramarital sex.

Testosterone levels do not rely on physical presence of a partner; testosterone levels of men engaging in same-city and long-distance relationships are similar.

Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.

INTERESTING.