The relation of thyroid autoimmunity to miscarriage is an important issue that has attracted the interest of many investigators. A number of papers have been published so far, which include healthy women, women with recurrent miscarriage and those undergoing assisted reproductive techniques. Most studies have shown a significant positive association between the presence of thyroid autoantibodies and miscarriage rate. It is of interest that women with high titers do not show a higher miscarriage rate when compared with women having low titers, although, there is no general agreement on this issue. There are three possible explanations for the assumed association of thyroid autoimmunity with miscarriage: 1) pregnancy loss is an epiphenomenon and not a direct effect of the thyroid autoantibodies, the presence of thyroid autoantibodies reflecting a generalized activation of the immune system; 2) delayed conception from the presence of thyroid autoantibodies; hence, when women with thyroid autoimmunity become pregnant, face a higher risk of miscarriage because of older age; and 3) the pregnancy loss is secondary to a subtle deficiency in thyroid hormone concentrations or a lower capacity of the thyroid to adequately adapt to the demands of pregnancy.

Systematic, regular high-volume endurance training induces significant metabolic adaptations in glucose and lipids metabolism, which seems to affect the negative impact of unhealthy nutrition, at least in animal models. The present study aimed to investigate the main determinants of body composition, blood glucose and lipids concentrations between middle-aged sedentary individuals (Sed) and well-trained endurance athletes (Run), both following an unhealthy high-fat diet. In thirty-five Sed (Age: 54.0 ± 6.6 yrs, Body Mass: 77.1 ± 10.5 kg, BMI: 31.3 ± 6.0 kg·m⁻²) and thirty-six Run (Age: 51.6 ± 5.2 yrs, Body Mass: 85.8 ± 3.4 kg, BMI: 23.2 ± 1.8 kg·m⁻²), body composition, nutritional intake, energy expenditure, resting metabolic rate (RMR), respiratory exchange ratio (RER), and blood glucose and lipids concentrations were evaluated. Multiple linear regression analyses revealed that body composition, blood glucose and lipids’ concentrations in the Run group were primarily determined by the energy expenditure (B: −0.879 to −1.254), while in the Sed group, by their energy intake (B:−0.754 to 0.724). In conclusion, it seems that in well-trained endurance middle-aged athletes, body composition, blood glucose, and lipids concentrations seem to be determined by their training-induced daily energy expenditure and not by their nutritional intake per se. At the same time, nutrition is the primary determinant in aged-matched sedentary individuals, even if they both follow high-fat diets.