Any facts to back that up? The story I hear more often [1] is the other way around. More men in medical studies, more often male animals in studies etc.
The lack of inclusion of women and minorities has historically been such a problem that it is now a term and condition of many awards from HHS:
"In addition, several OPDIVs have policies concerning the inclusion of women, minorities, and children as subjects in their grant-supported research. These policies, which implement Section 492B of the PHS Act, 42 U.S.C. 289 a-2, require that women and members of minority groups and their subpopulations be included in OPDIV-supported research projects involving human subjects, unless a clear and compelling rationale and justification establishes that inclusion is inappropriate with respect to the health of the subjects, the purpose of the research, or other circumstances. When these policies apply (as specified in the funding opportunity announcement), the applicant is required to address inclusion of these groups in the application narrative, and the applicant’s plans will be assessed as part of the objective (peer) review process. Failure to comply with this policy or to adequately address use of human subjects and animals may adversely affect the score for technical merit, which may result in the OPDIV not making an award."
"In addition, several OPDIVs have policies concerning the inclusion of women, minorities, and children as subjects in their grant-supported research. These policies, which implement Section 492B of the PHS Act, 42 U.S.C. 289 a-2, require that women and members of minority groups and their subpopulations be included in OPDIV-supported research projects involving human subjects, unless a clear and compelling rationale and justification establishes that inclusion is inappropriate with respect to the health of the subjects, the purpose of the research, or other circumstances. When these policies apply (as specified in the funding opportunity announcement), the applicant is required to address inclusion of these groups in the application narrative, and the applicant’s plans will be assessed as part of the objective (peer) review process. Failure to comply with this policy or to adequately address use of human subjects and animals may adversely affect the score for technical merit, which may result in the OPDIV not making an award."