Effects of reproductive state on olfactory sensitivity suggest odor specificity

Abstract

Previous studies of reproductive state and olfactory sensitivity in women have not directly compared thresholds for social and environmental odors. Here, we used successive dilutions presented in a staircase protocol to determine olfactory thresholds for androstadienone, a social odor produced by men, and rose, an environmental odor signaling a source of micronutrients essential for successful implantation, prenatal development and maternal health. Fertile women were more sensitive to the social than the environmental odor, while women using oral contraceptives, a non-fertile hormonal state similar to early pregnancy, were more sensitive to the environmental odor. This preliminary study sets the stage for further work on the interaction between hormonal states and sensitivity to specific odors with reproductive significance.

Introduction

Previous studies investigating the effects of different reproductive states on women’s olfactory sensitivity have not distinguished between their effects on social and environmental odors. We hypothesized that spontaneously ovulating women would be more sensitive to social than environmental odors, particularly in the fertile or estrogen dominant phase of the menstrual cycle, while women in progesterone dominant states would be more sensitive to environmental odors. Our hypothesis derives from the animal literature demonstrating that social cues enhance success of mating and conception (McClintock, 2003), whereas environmental odors, particularly those associated with nutrition, signal foods that reduce risk of perimplantation loss, prenatal malformations and malnutrition (Archunan and Dominic, 1989, Verma and Sherlin, 2001).

In this initial study, we choose rose (phenyl–ethyl alcohol, PEA) a well-characterized environmental odorant. Rose petals, leaves, roots, and hips are used in salads, conserves and medicines and they contain high concentrations of micronutrients essential for implantation, embryonic development and maternal health (e.g., Vitamins A and C in Rosa Canis; Archunan and Dominic, 1989, Grases et al., 1992). Androstadienone was chosen as the social odorant, as this steroid is present in the sweat, urine and semen of men (Gower and Ruparelia, 1993), and typically detectable as an odor in concentrations over 211 μM (Lundstrom et al., 2003b). Even in very high concentrations neither androstadienone (Lundstrom et al., 2003b) nor PEA (Doty, 2003) activates the trigeminal system, which ensured that only olfactory sensitivity was assessed by the method used here. We compared women who were ovulating spontaneously to non-ovulating women using oral contraceptives. These contraceptives create a hormonal profile with equally high levels of estrogens and progestins, more similar to the luteal phase and early pregnancy than to the estrogen dominant follicular phase (Mucci et al., 2004).