Chronic pain is gender-related, since there is a clear predominance of one sex with respect to the other in most pain syndromes. Gonadal hormones are known to affect the occurrence and incidence of pain. Transsexuals receive cross-sex hormones to develop and maintain somatic characteristics of the opposite sex: male to female transsexuals (MtF) are administered estrogens and anti-androgens, while female to male transsexuals (FtM) are administered androgens. Hence, these subjects represent a model to study the relationship between sex hormones and pain. Questionnaires dealing with sociodemographic data and pain (occurrence, frequency, duration, intensity, location and associated symptoms) were administered to both MtF and FtM transsexuals under hormone treatment for sex reassignment for at least 1 year. Forty-seven MtF and 26 FtM completed the questionnaires. Fourteen of the 47 MtF (29.8%) reported painful conditions, which in 11 subjects were not present before the beginning of hormone treatment. Pain consisted mainly of headaches and breast and musculoskeletal pain. Five subjects suffered from more than one pain condition. Sixteen of the 26 FtM (61.5%) reported pain. In 11 subjects, the pain was present before the beginning of hormone intake, and in 6 of them it improved after testosterone administration. These data suggest that marked changes in sex hormones affect the occurrence of pain in a high percentage of humans but not in all of them. Whether these effects are due to peripheral or central actions of sex steroids is unknown.

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In order to investigate the roles of near N-terminus Tyr, Cys, and Ser residues in the activity of bacterial glutathione transferase (GSTB1-1) site-directed mutagenesis was used to replace the following residues: Tyr-4, Tyr-5, Ser-9, Cys-10, Ser-11, and Ser-13. The results presented here show that, unlike all other alpha, mu, pi, theta and sigma classes of glutathione transferases so far investigated, GSTB1-1 does not utilise any Tyr, Ser or Cys residue to activate glutathione. These results also suggest that the bacterial glutathione transferases may require classification into their own class.z 1998 Federation of European Biochemical Societies.

Background: Besides functioning as chemosensors for a broad range of endogenous and synthetic ligands, transient receptor potential vanilloid (TRPV) 1-4 channels have also been related to capsaicin (TRPV1), pain, and thermal stimuli perception, and itching sensation (TRPV1-4). While the expression of the TRPV1-4 genes has been adequately proved in skin, sensory fibres and keratinocytes, less is known about TRPV3 and TRPV4 expression in human blood cells.

Macrophage migration inhibitory factor (MIF) is a cytokine produced by neuroendocrine and immune tissues that possesses several characteristics of a neuroendocrine mediator. Chronic pain is known to affect and to be affected by neuroendocrine and immune mechanisms. In the present study, the plasma levels of MIF and several hormones (cortisol, estradiol, testosterone) were determined to evaluate their mutual behaviour in controls and in chronic pain patients. Blood samples were collected from males and females divided into groups depending on their age (younger or older than 55) and health condition: (1) pain-free control subjects; (2) chronic non-malignant pain subjects. Moreover, two additional groups were added to evaluate the effects of short- and long-term opioid administration: (3) short-term opioid-treated chronic pain patients and (4) long-term opioid-treated chronic pain patients (longer than 6 months). MIF in control/younger men was higher than in all the other control and chronic pain groups. MIF was lower in pain patients than in controls of both sexes. MIF was not changed by morphine administration; its levels remained lower in opioid-treated subjects than in controls after both short- and long-lasting administration. Chronic pain changed hormone plasma levels differently in male and female patients. MIF was positively correlated with testosterone and negatively with estradiol. These results demonstrate sex differences in the younger men and women and a strong pain-induced decrease of MIF availability. These findings suggest the involvement of this cytokine in the sex differences observed in chronic pain conditions.