Browsing by Person "Sharp, M. A."

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Establishing circadian rhythm profiles for salivary testosterone in women: evidence of decline during ageing
(2006) Al-Dujaili, Emad A. S.; Sharp, M. A.
Androgens are increasingly known to play an important role in female health, development and well being. Alongside a controversial increase in androgen therapy there is a realisation that what actually constitutes androgen insufficiency is poorly understood. The aim of this study was to establish circadian profiles for salivary testosterone in healthy women from the age of 19 through 69 year old at 3 points during the menstrual cycle. Females were subdivided into these groups: 19-29, 30-39, 40-49 (peri- and post-menopausal), 50-59 and 60-69 years were investigated. The study was approved by the University College Ethical Committee and all subjects provided 8 saliva samples per day on the 4th, 14th and 21th day of their cycle. Post-menopausal women collected saliva samples on the 4th, 14th and 21th day of the calendar month. The women were not on any hormonal medication such as the contraceptive pill and HRT; nor did they suffer from any major illness. Testosterone levels were estimated using our in-house highly sensitive and specific ELISA method. The results indicated that female salivary testosterone concentration showed a circadian rhythm similar to that found in males, though at much lower levels. Perhaps more importantly, throughout the course of the day testosterone levels were highly variable with episodic fluctuations of individual data points exceeding the 09.00 hours levels by up to 90% on some occasions, indicating a role for the hormone in reproduction and sexual health. There was marked variation in testosterone concentration between day 4, 14 and 21 of the cycle, though not statistically significant except for the age group of 30-39 year (P<0.02, one-way repeated measure ANOVA). However, a significant decline in female salivary testosterone levels after the age of 39 years was evident. Day 4 of the cycle always exhibited near absence of salivary testosterone circadian rhythm. In contrast, day 21 testosterone values showed the best clear indication of the circadian rhythm profile compared to day 4 of the cycle. In conclusion, our study has established circadian profiles for female salivary testosterone and indicated that the testosterone levels were seriously low in some post-menopausal women and those above the age of 50 years that may justify some intervention to improve the health and well being of women.
Evidence for the stress-linked immunocompetence handicap hypothesis in human male faces
(2011-03-07) Moore, F. R.; Cornwell, R. E.; Law Smith, M. J.; Al-Dujaili, Emad A. S.; Sharp, M. A.; Perrett, D. I.
The stress-linked immunocompetence handicap hypothesis (SL-ICHH) of sexual selection incorporates a role of the stress hormone corticosterone (C; cortisol in humans) in relationships between testosterone (T), immunity and secondary sexual trait expression. In support of this, C has been shown to mediate and moderate relationships between T and immune response and to be inversely related to attractiveness in some avian species. We predicted that female preferences for cues to T in human male faces would be contingent upon co-occurring cortisol levels. In study 1, we tested relationships between Tand cortisol and attractiveness, masculinity and health ratings of raw male faces. We found cortisol to be inversely related to attractiveness. In study 2, we tested female preferences for male faces that were parametrically manipulated on the basis of cues to naturally co-occurring levels of T and cortisol across the menstrual cycle. Women preferred cues to low cortisol in general and in the fertile phase of the cycle, and there was an interaction between Tand cortisol in general and in the non-fertile phase. Results were consistent with the SL-ICHH but not the original immunocompetence handicap model: females expressed preferences for cues to cortisol but not for cues to T, except in interaction with the stress hormone. Results inform the SL-ICHH by demonstrating female preferences for low cortisol and the nature of its interaction with T in humans, as well as indicating the traits that may be signalled by different combinations of the hormones including immune response, current health and resource acquisition characteristics. 2010 The Royal Society.
Raised salivary testosterone in women is associated with increased attraction to masculine faces
(Elsevier, 2007-08) Welling, L.; Jones, B.; Debruine, L.; Conway, C. A.; Lawsmith, M.; Little, A.; Feinberg, D.; Sharp, M. A.; Al-Dujaili, Emad A. S.
Women's preferences for masculinity in men's faces, voices and behavioral displays change during the menstrual cycle and are strongest around ovulation. While previous findings suggest that change in progesterone level is an important hormonal mechanism for such variation, it is likely that changes in the levels of other hormones will also contribute to cyclic variation in masculinity preferences. Here we compared women's preferences for masculine faces at two points in the menstrual cycle where women differed in salivary testosterone, but not in salivary progesterone or estrogen. Preferences for masculinity were strongest when women's testosterone levels were relatively high. Our findings complement those from previous studies that show systematic variation in masculinity preferences during the menstrual cycle and suggest that change in testosterone level may play an important role in cyclic shifts in women's preferences for masculine traits.
Salience of emotional displays of danger and contagion in faces is enhanced when progesterone levels are raised
(Elsevier, 2007-02) Conway, C. A.; Jones, B.; Debruine, L.; Welling, L.; Lawsmith, M.; Perrett, D. I.; Sharp, M. A.; Al-Dujaili, Emad A. S.
Findings from previous studies of hormone-mediated behavior in women suggest that raised progesterone level increases the probability of behaviors that will reduce the likelihood of disruption to fetal development during pregnancy (e.g. increased avoidance of sources of contagion). Here, we tested women's (N = 52) sensitivity to potential cues to nearby sources of contagion (disgusted facial expressions with averted gaze) and nearby physical threat (fearful facial expressions with averted gaze) at two points in the menstrual cycle differing in progesterone level. Women demonstrated a greater tendency to perceive fearful and disgusted expressions with averted gaze as more intense than those with direct gaze when their progesterone level was relatively high. By contrast, change in progesterone level was not associated with any change in perceptions of happy expressions with direct and averted gaze, indicating that our findings for disgusted and fearful expressions were not due to a general response bias. Collectively, our findings suggest women are more sensitive to facial cues signalling nearby contagion and physical threat when raised progesterone level prepares the body for pregnancy.