One Major Advantage of this System The thyroid gland is capable of storing many weeks worth of thyroid hormone (coupled to thyroglobulin). If no iodine is available for this period, thyroid hormone secretion will be maintained.
Actions of Thyroid Hormones Thyroid hormones are essential for normal growth of tissues, including the nervous system. Lack of thyroid hormone during development results in short stature and mental deficits (cretinism). Thyroid hormone stimulates basal metabolic rate. What are the specific actions of thyroid hormone on body systems?
Actions of Thyroid Hormone Required for GH and prolactin production and secretion Required for GH action Increases intestinal glucose reabsorption (glucose transporter) Increases mitochondrial oxidative phosphorylation (ATP production) Increases activity of adrenal medulla (sympathetic; glucose production) Induces enzyme synthesis Result: stimulation of growth of tissues and increased metabolic rate. Increased heat production (calorigenic effect)
Effects of Thyroid Hormone on Nutrient Sources Effects on protein synthesis and degradation: increased protein synthesis at low thyroid hormone levels (low metabolic rate; growth) increased protein degradation at high thyroid hormone levels (high metabolic rate; energy) Effects on carbohydrates: low doses of thyroid hormone increase glycogen synthesis (low metabolic rate; storage of energy) high doses increase glycogen breakdown (high metabolic rate; glucose production)
Age or population group a U.S. Institute of Medicine Age or population group c World Health Organization Infants 0–12 months b 110-130 Children 0-5 years 90 Children 1-8 years 90> Children 6-12 years 120 Children 9-13 years 120> Adults ≥14 years 150 Adults >12 years 150 Pregnancy 220 Pregnancy 250 Lactation 290 Lactation 250 Recommendations for iodine intake (µg/day) by age or population group a Recommended Daily Allowance. b Adequate Intake. c Recommended Nutrient Intake.
The spectrum of iodine deficiency disorders, IDD
ผลกระทบจากการขาดไอโอดีน เมื่อตั้งครรภ์ J Clin Endocrinol Metab.J Clin Endocrinol Metab. 2013 May;98(5):1954-62. doi: 10.1210/jc.2012-4249. Epub 2013 Apr 30. Mild iodine deficiency during pregnancy is associated with reduced educational outcomes in the offspring: 9-year follow-up of the gestational iodine cohort. Hynes KLHynes KL, Otahal P, Hay I, Burgess JROtahal PHay IBurgess JR CONCLUSIONS: This study provides preliminary evidence that even mild iodine deficiency during pregnancy can have long-term adverse impacts on fetal neurocognition that are not ameliorated by iodine sufficiency during childhood. ผลการขาดไอโอดีนแม้เพียงเล็กน้อยระหว่างตั้งครรภ์ มีผลระยะยาวต่อ ระดับสติปัญญาของเด็ก แม้ว่าเมื่อคลอดมาแล้วจะไม่ขาดไอโอดีนก็ ตาม
Iodine StatusGeneral Population ( g/L) Pregnant and lactating women ( g/L) School children ≥6 years old ( g/L) Excessive* ≥ 300 ≥ 500 ≥ 300 Above requirements 200-299250-499200-299 Iodine Sufficient 100-199150-249100-199 Mild Iodine Deficiency 50-99<15050-99 Moderate Iodine Deficiency 20-49<20-4920-49 Severe Iodine Deficiency <20 WHO/UNICEFF/ICCIDD criteria for assessing population iodine status using population median urinary iodine concentration *The term “excessive” means in excess of the amount required to prevent and control iodine deficiency. Values in this table are sourced from WHO/UNICEF/ICCIDD (2007a)