Investigating the Impact of Selenium Deficiency on Thyroid Function in Iodine-Deficient New Zealand Women | Chapter 8 | Achievements and Challenges of Medicine and Medical Science Vol. 7

This narrative review aimed to present the current situation in New Zealand women who are mostly selenium and iodine deficient across their lifespans. The prevalence of thyroid disease in New Zealand women is about 5% and increased to 7%-14% in women over 50 years of age. The importance of selenium is widely recognised. Selenium plays a crucial role in metabolic, immune-endocrine, and cellular homeostasis, owing to its antioxidant and anti-inflammatory properties. Changes in selenium status may affect immune response, neurodegeneration, cardiovascular disease, and cancer. The biological actions of selenium are mostly mediated through the expression of at least 30 selenoproteins, coded by 25 genes with the 21st amino acid selenocysteine at their active centre. Selenoenzymes, selenoprotein P and glutathione peroxidase are present in human plasma and can be used as a biomarker of selenium nutritional status. The thyroid gland has a high tissue concentration of the essential micronutrient selenium (Se), more than the liver, skeletal muscles or any other organ or tissue. Thyroid dysfunction is a significant health issue in New Zealand, with women being 4.5 times more likely than men to have thyroid disorders.  For the North Island, but not for the South Island, selenium intakes have improved after increased importation of high-Se Australian and other imported wheat, because the soil in New Zealand is poor in selenium. According to the most recent 2008/09 New Zealand Nutrition Survey (NZANS), selenium intakes increased from 1997 to 2008/09. The 2023 study indicated that overall plasma selenium concentrations were higher in those living in the Nort Island (93µg/L) than in those (85.4µg/L) in the South Island.   Plasma selenium concentrations around 95 µg/L are sufficient to saturate glutathione peroxidase activity although more selenium is required to saturate selenoprotein P than to optimise GPx. In New Zealand women low plasma levels of selenium intake and low levels in the food supply have been observed in women of childbearing age and postmenopausal. Inadequate selenium status was noted in postpartum women, breastfeeding women and their infants. This situation somehow creates a vicious cycle of selenium deficiency. The finding of low plasma selenium concentrations in women who were also iodine deficient was an indicator of high thyroid dysfunction which might present itself with overt hypothyroidism, subclinical hyperthyroidism and thyroid autoimmune disorder. Current studies noted that most healthy elderly women had selenium intakes marginal to iodine intakes. Due to a lack of oestrogen, they are put at risk of compromised thyroid function. Selenium supplementation with selenomethionine (SeMet) or selenium selenite might improve selenium deficiency and slow thyroid destruction by thyroid autoantibodies. Hormone replacement therapy and antidepressant and antianxiety medication cannot decrease the symptoms of thyroid dysfunction.

 

Author (s) Details

 

Ljiljana Jowitt
Faculty of Health and Environmental Sciences, The School of Public Health and Interdisciplinary Studies, AUT University, 90 Akoranga Drive, North Shore Campus, AZ Building Level 4, P.O. Box 92006, 1142, Auckland, New Zealand.

 

 

Please see the book here:- https://doi.org/10.9734/bpi/acmms/v7/2659