High doses of Se supplements in pregnant animals might disturb the Zn:Cu ratio and lead to Zn reduction; in such treatment cases, Zn levels should be monitored. Further studies are needed to confirm these interactions.In the regions (e.g. various regions within North America) where low selenium soil levels lead to low concentrations in the plants, some animal species may be deficient unless selenium is supplemented with diet or injection. Ruminants are particularly susceptible. In general, absorption of dietary selenium is lower in ruminants than other animals, and is lower from forages than from grain. Ruminants grazing certain forages, e.g., some white clover varieties containing cyanogenic glycosides, may have higher selenium requirements, presumably because cyanide is released from the aglycone by glucosidase activity in the rumen and glutathione peroxidases is deactivated by the cyanide acting on the glutathione moiety. Neonate ruminants at risk of white muscle disease may be administered both selenium and vitamin E by injection; some of the WMD myopathies respond only to selenium, some only to vitamin E, and some to either. Health effects
The effects of selenium intake on cancer have been studied in several clinical trials and epidemiologic studies in humans. Selenium may have a chemo-preventive role in cancer risk as an anti-oxidant, and it might trigger the immune response. At low levels, it is used in the body to create anti-oxidant selenoproteins, at higher doses than normal it causes cell death.Selenium (in close interrelation with iodine) plays a role in thyroid health.
Thymus hyperplasia refers to an enlargement ("hyperplasia") of the thymus.It is not always a disease state. The size of the thymus usually peaks during adolescence and atrophies in the following decades. Before the immune function of the thymus was well understood, the enlargement was sometimes seen as a cause for alarm, and justification for surgical reduction. This approach is much less common today. It can be associated with myasthenia gravis. Magnetic Resonance Imaging can be used to distinguish it from thymoma. Thymic hyperplasia
Thymic hyperplasia can be divided into three groups namely, those without any pre-existing medical condition, those recovering from a pre-existing medical condition such as pneumonia, corticosteroid therapy, radiation therapy, chemotherapy, surgery, and burns, and those with other disorders such as  hyperthyroidism, sarcoidosis, or pure red cell aplasia. References


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