Physicians as guardians of science have an obligation to teach the facts of life to our patients and our legislators. And today the need to dispel ignorance of biologic facts is more urgent than ever. Just as President Obama is deferring legislation on marriage to the states, I will defer the issue of whether the government can or should regulate marriage to legal scholars and our duly elected representatives. However, when legislators pass laws that define marriage as a union between a man and a woman, I want to be very, very sure that they know biology and are fully informed on just who is a man or who is a woman. If legislators say they are against same sex marriage, do they know what they are talking about?

I am an endocrinologist who deals with issues of sex determination and abnormalities of the reproductive system. Although one would think that that certain difference between a man and a woman is obvious ? it is not. Determining who is a man and who is a woman can be simple on the surface and in the vast majority of cases a surface test is all that is needed. This was the accepted Olympic standard when those muscular East German women were winning all those medals. Looking like a man or a woman however, is not the end of the story. In biologic terms sex determination is a complex process that proceeds from genes to gonads to outward body shape and appearance to behavior and finally to society. What chromosomes does a person have? What is the expression of those genes? What gonad is formed? What external genitalia and secondary sexual characteristics develop? What behavior is manifest? And the final test: what do you and I feel towards this individual?

Let us review a couple of cases to highlight the problem. Normal males have one X and one Y chromosome; normal females are XX. What happens when an XY individual has a mutation that interferes with the function of the receptor for testosterone? This is the case in a condition called testicular feminization. The XY genes produces testicles and the testicles produce male hormone but the body does not respond: the message is there; it just can?t be heard or acted on. Individuals with testicular feminization look and act female. They develop breasts, society treats them as women; they are interested in men; they marry but they are infertile. When this XY woman marries an XY man is this a same sex marriage? By the same token there are XX individuals who are men in every respect other than their genotype. If she/he marries an XX woman is this a same sex marriage? Should an XY individual with testicular feminization be permitted to marry an XX woman? Should an XX man be permitted to marry an XY man?

This is but the tip of a biologic iceberg that leads to the question who determines sex and why is it being determined? The genetic and chemical code that determines sexual orientation is yet to be fully delineated but I am sure that it will be fundamentally the same as in the examples above. Ignorance of the biologic underpinnings of sexual orientation should not be a reason to legislate against its genetic varieties and phenotypes. The lesson is this: My patients with testicular feminization are happily married to men. They are raising healthy families. The government is none the wiser — nor should it be. As physicians we have an obligation to share our knowledge with our legislators and the public to inform the decisions that they make.

Arthur Chernoff is Chair, Division of Endocrinology, Albert Einstein Medical Center.

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