The deleterious effects of chronic dietary consumption of foods with high lectin contents is receiving a great deal of attention these days. Many common plant foods contain lectins which the plant employs as defense mechanisms. Gluten is a lectin. When humans consume such foods, the lectins in them deploy n the gut. The immediate mechanism of their action is to provoke an auto-immune reaction by way of molecular mimicry. Lectins (there are a great many) are functionally indistinguishable from proteins and bind to cell receptors causing havoc with hormone regulation.
In the 1960s general practitioners (there were no family medicine specialists then) knew that empirically that putting women on thyroid medication helped reproductive function. Interestingly, thyroid medications were sold over the counter in the 1960s.
Soon after this, the FDA recalled the non-prescriptive drugs into prescriptive drugs categories and then required a blood test before patients could be medicated. Dr. Steven Langer, a family physician thats published several books on the topic of infertility and thyroid related illnesses suggests that the TSH (thyroid stimulating hormone) levels must be assessed.
In addition, medical databases, such as PubMed (a service of the U.S. National Library of Medicine and the National Institutes of Health) have more and more research papers being published about sub-clinical hypothyroidism and infertility.