In response to inquires about an association between "visual acuity" and thyroid hormones we have compiled a short list of relevant papers on the subject of vision and thyroid function.
These questions arose from yet another study done by the York team around Christine Till that failed - once again - to account for the high iodine intake in the MIREC mothers (Krzeczkowski et al., 2023).
- Krzeczkowski JE, Hall M, Saint-Amour D, Oulhote Y, McGuckin T, Goodman C, Green R, Muckle G, Lanphear B, Till C - "Prenatal fluoride exposure, offspring visual acuity and autonomic nervous system function in 6-month-old infants" Environment International
Available online 27 November 2023, 108336
https://www.sciencedirect.com/science/a ... 2023006098
It is well established that thyroid hormones (TH) are essential for the development of structures necessary for visual processing (Roberts et al., 2006; Pessôa et al., 2008; Forrest et al., 2002; Mirabella et al., 2005; Ng et al., 2001).
The critical requirement of TH for the development of the ANS (autonomous nervous system) also goes without saying.
Hence, a considerable body of literature has been published on the effects of thyroid status on vision, encompassing the impact of maternal thyroid status on eye function in offspring, including 'visual acuity'—a measure of the clarity or sharpness of one's vision.
Besides a brief mention of the work by Brusseau et al. (2020), there is no discussion of TH involvement in the paper by the York team. As stated, no adjustment is made for the high iodine intake by the MIREC mothers, nor the fact mentioned that high iodine intake might be responsible for all effects observed.
Until this issue is addressed, all the York/MIREC papers on fluoride remain suspect.
PFPC Canada
Vision
Bell J - "Mom’s Hypothyroidism Affects Baby’s Eye Function" Clinical Endocrinology News, November 2007
https://cdn.mdedge.com/files/s3fs-publi ... ain_17.pdf
Fink C, Vedin AM, Garcia-Filion P, Ma NS, Geffner ME, Borchert M - "Newborn thyroid-stimulating hormone in children with optic nerve hypoplasia: associations with hypothyroidism and vision" J AAPOS 16(5):418-23 (2012). doi: 10.1016/j.jaapos.2012.05.012
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3481172/
"Those diagnosed with hypothyroidism had lower median NBS TSH levels than did euthyroid subjects (3.2 vs 4.5 μIU/mL; P = 0.006) and significantly worse quantitative vision outcomes (median visual acuity, logMAR 3.0 vs 1.0; P = 0.039)."
Forrest D, Reh TA, Rüsch A - "Neurodevelopmental control by thyroid hormone receptors" Curr Opin Neurobiol 12(1):49-56 (2002). doi: 10.1016/s0959-4388(02)00289-1
https://www.sciencedirect.com/science/a ... 8802002891
"In addition, deiodinase enzymes that regulate levels of the main active form of thyroid hormone, T3, are likely to cooperate closely with TRs in specifying a localized and timely response to thyroid hormones in target tissues. Some of the most sensitive processes controlled by these pathways are in the auditory and visual sensory systems."
Harpavat S, Cepko CL - "Thyroid hormone and retinal development: an emerging field" Thyroid 13(11):1013-9 (2003). doi: 10.1089/105072503770867183
https://www.liebertpub.com/doi/10.1089/ ... 3770867183
Jankauskiene J, Jarusaitiene D - "Assessment of visual acuity, refraction changes, and proptosis in different ages of patients with thyroid diseases" Int J Endocrinol 2012:643275 (2012) doi: 10.1155/2012/643275
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3502845/
"The data we have found suggest that Graves' disease in children, teenagers, and adults has influence on vision acuity, refraction, and eye proptosis."
Jones I, Srinivas M, Ng L, Forrest D - "The thyroid hormone receptor beta gene: structure and functions in the brain and sensory systems" Thyroid 13(11):1057-68 (2003). doi: 10.1089/105072503770867228
https://www.liebertpub.com/doi/10.1089/ ... 3770867228
Kurtul BE, Ozer PA, Kabatas EU, Gürkan A, Aycan Z - "Ophthalmic Manifestations in Children With Congenital Hypothyroidism" J Pediatr Ophthalmol Strabismus 53(1):29-34 (2016) doi: 10.3928/01913913-20160113-06
https://journals.healio.com/doi/10.3928 ... 0160113-06
"Ophthalmic pathology was determined in 40.4% (49 of 121) of patients with congenital hypothyroidism. Systemic abnormalities were observed in 74.3% (90 of 121) of the children, among which 47.1% (57 of 121) were congenital heart defects and 38.0% (46 of 121) were neurologic abnormalities. A high prevalence of Down syndrome (17.3%; 21 of 121) and atopic dermatitis (8.2%; 10 of 121) was detected among patients with congenital hypothyroidism."
Ma H, Yang F, York LR, Li S, Ding XQ - "Excessive Thyroid Hormone Signaling Induces Photoreceptor Degeneration in Mice" eNeuro. 10(9):ENEURO.0058-23.2023 (2023) doi: 10.1523/ENEURO.0058-23.2023
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10481642/
Mirabella G, Westall CA, Asztalos E, Perlman K, Koren G, Rovet J - "Development of contrast sensitivity in infants with prenatal and neonatal thyroid hormone insufficiencies" Pediatr Res 57(6):902-7 (2005) doi: 10.1203/01.PDR.0000157681.38042.B4
https://www.nature.com/articles/pr2005166
"Animal studies have shown that TH is necessary for the development of primary visual structures—the retina, magnocellular neurons in the lateral geniculate nucleus of the thalamus, and the primary visual cortex —with timing being earlier for retina than for thalamus and for thalamus than for cortex. Given that TH is important for neurodevelopmental processes along this pathway, a lack of TH during these periods would disrupt such development...In the retina, TH is needed for the differentiation of cones versus rods, specific cone subtypes, and retinal oligodendrocyte precursor cells and for the production of essential proteins. Animal models demonstrate that when TH is lacking at a particular time prenatally, visual development and functioning will be impaired. Although comparable evidence is not available on humans, visual processing deficits in children with prenatal or neonatal TH insufficiencies suggest that the human visual system may also be vulnerable to an early lack of TH insufficiency."
Ng L, Hurley JB, Dierks B, Srinivas M, Salto C, Vennstrom B, Reh TA, Forrest D - "A thyroid hormone receptor that is required for the development of green cone photoreceptors" Nat Genet 27: 94–98 (2001)
https://www.nature.com/articles/ng0101_94
Pessôa CN, Santiago LA, Santiago DA, Machado DS, Rocha FA, Ventura DF, Hokoç JN, Pazos-Moura CC, Wondisford FE, Gardino PF, Ortiga-Carvalho TM - "Thyroid hormone action is required for normal cone opsin expression during mouse retinal development" Invest Ophthalmol Vis Sci 49(5):2039-45. doi: 10.1167/iovs.07-0908 (2008)
https://iovs.arvojournals.org/article.a ... id=2125387
Roberts MR, Srinivas M, Forrest D, Morreale de Escobar G, Reh TA - "Making the gradient: thyroid hormone regulates cone opsin expression in the developing mouse retina" Proc Natl Acad Sci USA 103:6218–6223 (2006)
https://www.pnas.org/doi/10.1073/pnas.0509981103
Rovet J, Simic N - "The role of transient hypothyroxinemia of prematurity in development of visual abilities" Semin Perinatol 32(6):431-7 (2008) doi: 10.1053/j.semperi.2008.09.009
https://pubmed.ncbi.nlm.nih.gov/19007682/
"In the second cohort born 23 to 35 weeks gestation, THOP severity was negatively correlated with attention at 3 months corrected age (Study 3) and contrast sensitivity and color vision at 6 months corrected age (Study 4). These findings therefore suggest that thyroid hormone is necessary for the development of early visual abilities and that THOP may partially explain the visual deficits of preterm infants."
Rovet J - "Congenital Hypothyroidism: Long-Term Outcome" Thyroid 9(7):741–748 (1999) doi:10.1089/thy.1999.9.741
"Since 1980, we have been following a large cohort of Toronto-based children with congenital hypothyroidism identified by newborn screening from infancy to adolescence. Early findings revealed a 5-10-point decline in IQ, poorer visuomotor and visuospatial abilities, delayed speech and language development, selective neuromotor deficiencies, and poorer attention and memory skills, which were correlated with different disease and treatment factors."
Simic N, Westall C, Astzalos EV, Rovet J - "Visual abilities at 6 months in preterm infants: impact of thyroid hormone deficiency and neonatal medical morbidity" Thyroid 20(3):309-15 (2010). doi: 10.1089/thy.2009.0128
https://pubmed.ncbi.nlm.nih.gov/20144040/
"Our findings signify that some of the weak visual abilities in preterm infants can be accounted for, in part, by their reduced TH levels in the early postnatal period."
Simic N, Khan S, Rovet J - "Visuospatial, visuoperceptual, and visuoconstructive abilities in congenital hypothyroidism" J Int Neuropsychol Soc 19(10):1119-27 (2013). doi: 10.1017/S1355617713001136
https://www.cambridge.org/core/journals ... 4780CD936F
Su PY, Huang K, Hao JH, Xu YQ, Yan SQ, Li T, Xu YH, Tao FB - "Maternal thyroid function in the first twenty weeks of pregnancy and subsequent fetal and infant development: a prospective population-based cohort study in China" J Clin Endocrinol Metab 96(10):3234-41 (2011). doi: 10.1210/jc.2011-0274
https://academic.oup.com/jcem/article/9 ... 34/2834923
"Subclinical hypothyroidism was associated with increased fetal distress, preterm delivery, poor vision development, and neurodevelopmental delay."
Zimmerman D - "Fetal and neonatal hyperthyroidism" Thyroid 9(7):727-33 (1999). doi: 10.1089/thy.1999.9.727
https://pubmed.ncbi.nlm.nih.gov/10447021/
"Fetal heart rate and fetal growth should be monitored."
Zoeller RT, Rovet J - "Timing of thyroid hormone action in the developing brain: clinical observations and experimental findings" J Neuroendocrinol. 16(10):809-18 (2004). doi: 10.1111/j.1365-2826.2004.01243.x
https://onlinelibrary.wiley.com/doi/10. ... 04.01243.x
"If the TH deficiency occurs early in pregnancy, the offspring display problems in visual attention, visual processing (i.e. acuity and strabismus) and gross motor skills. If it occurs later in pregnancy, children are at additional risk of subnormal visual (i.e. contrast sensitivity) and visuospatial skills, as well as slower response speeds and fine motor deficits."
Heart Rate
Bhupathi R, Kothari SS, Gupta AK, Menon PS - "Cardiac function in hypothyroid children: effect of replacement therapy." Indian Pediatr 36(8):779-84 (1999)
https://pubmed.ncbi.nlm.nih.gov/10742732/
"Subtle evidence of alteration of myocardial function is thus seen in children with primary hypothyroidism which reverses with treatment."
Brusseau V, Tauveron I, Bagheri R, Ugbolue UC, Magnon V, Navel V, Bouillon-Minois JB, Dutheil F - "Heart rate variability in hypothyroid patients: A systematic review and meta-analysis" PLoS One 17(6):e0269277 (2022). doi: 10.1371/journal.pone.0269277
https://journals.plos.org/plosone/artic ... ne.0269277
"There was a decrease in SDNN, RMSSD...HRV alteration increased with severity of hypothyroidism...Conclusions: Hypothyroidism is associated with a decreased HRV, that may be explained by molecular mechanisms involving catecholamines and by the effect of TSH on HRV."
Cai Z, Dai M, Zhang Y, Zhong H, Tan T, Bao M - "Imbalance of cardiac autonomic nervous activity and increase of ventricular repolarization dynamicity induced by thyroid hormones in hyperthyroidism" Auton Neurosci 213:86-91 (2018). doi: 10.1016/j.autneu.2018.06.006
https://www.autonomicneuroscience.com/a ... 4/fulltext
Candido AC, Vieira AA, de Souza Ferreira E, Moreira TR, do Carmo Castro Franceschini S, Cotta RMM - "Prevalence of Excessive Iodine Intake in Pregnancy and Its Health Consequences: Systematic Review and Meta-analysis" Biol Trace Elem Res. 2022 Aug 26. doi: 10.1007/s12011-022-03401-5. Epub ahead of print. PMID: 36018544.
https://pubmed.ncbi.nlm.nih.gov/36018544/
"The prevalence of excessive iodine intake in 10,736 pregnant women in different regions of the world was 52%. The main implications for pregnant women were hypothyroxinemia, hypothyroidism, and hyperthyroidism. For the newborn, macrosomia and thyroid dysfunction."
Echeverría JC, Solís LI, Pérez JE, Gaitán-González MJ, Rivera IR, Mandujano M, Sánchez MC, González-Camarena R - "The autonomic condition of children with congenital hypothyroidism as indicated by the analysis of heart rate variability" Auton Neurosci 167(1-2):7-11 (2012) doi: 10.1016/j.autneu.2011.10.007. Epub 2011 Nov 22. PMID: 22112613.
"We found that the HRV obtained from children with CH is diminished as suggested by statistical differences (p<0.05) in the following parameters: RMSDD, pNN20, total power, LF and HF. "
Hoshi RA, Santos IS, Dantas EM, Andreão RV, Mill JG, Duncan BB, Schmidt MI, Lotufo PA, Bensenor I - "Diabetes and subclinical hypothyroidism on heart rate variability" Eur J Clin Invest 50(12):e13349 (2020). doi: 10.1111/eci.13349
https://pubmed.ncbi.nlm.nih.gov/32654127/
Hoshi RA, Andreão RV, Santos IS, Dantas EM, Mill JG, Lotufo PA, Bensenor IM - "Linear and nonlinear analyses of heart rate variability following orthostatism in subclinical hypothyroidism" Medicine (Baltimore) 98(4):e14140 (2019) doi: 10.1097/MD.0000000000014140
https://pubmed.ncbi.nlm.nih.gov/30681577/
Mavai M, Bhandari B, Singhal A, Mathur SK - "Cardiac Autonomic Modulation and Anti-Thyroid Peroxidase (TPO) Antibodies in Subclinical Hypothyroidism: Does a Correlation Exist?" Cureus 13(10):e18844 (2021) doi: 10.7759/cureus.18844
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8597668/
"Decreased HRV was observed in the anti-TPOAb positive group when compared to the antibody-negative and control groups. Significant positive correlation of anti-TPOAb with TSH, LFnu, LF/HF and negative correlation with SDNN, RMSSD, pNN50, SD1, SD1/SD2, HFnu, and TP of HRV was observed."
Öner T, Özdemir R, Doksöz Ö, Yozgat Y, Karadeniz C, Demirpençe S, Yılmazer MM, Büyükinan M, Meşe T, Tavlı V - "Cardiac Function in Newborns with Congenital Hypothyroidism: Association with Thyroid-Stimulating Hormone Levels" J Clin Res Pediatr Endocrinol 7(4):307-11 (2015) doi: 10.4274/jcrpe.1969
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4805224/
"Impairment in left ventricular systolic function and increased risk of arrhythmia were observed in newborn infants with congenital hypothyroidism. TSH level was associated with heart rate and interventricular septum velocity."
Trapali C, Dellagrammaticas HD, Nika A, Iacovidou N - "A unique case of reversible myocardial ischemia in a hyperthyroid neonate" Pediatr Cardiol. 29(1):180-2 (2008) doi: 10.1007/s00246-007-9060-8
https://pubmed.ncbi.nlm.nih.gov/17912485/
Birth Weight
As noted by Miriam Stellenberg, Krzeczkowski et al. also state the following:
Increased birth weight is, of course, also related to thyroid function, and documented to be associated with increased iodine intake from supplements during pregnancy (i.e. Dong et al., 2021). The average average iodine intake of MIREC women was 444 μg/day, WHO recommendation is 250 μg/day. 88% of the pregnant women took prenatal supplements containing approx. 220 µg of potassium iodide."Infants born in fluoridated regions had a higher birthweight (3527.22 g; SD=498.52) than those born in non-fluoridated regions (3419.72 g; SD=519.62)."
We have been writing about the association of fluoride with decreased birth weight and PTD since 1996, and much information on this subject can be found on our website.
Fluoride, Thyroid & Preterm Birth/LBW (2000)
viewforum.php?f=48
Dong J, Liu S, Wang L, Zhou X, Zhou Q, Liu C, Zhu J, Yuan W, Xu WY, Deng J - "Iodine monitoring models contribute to avoid adverse birth outcomes related more than adequate iodine intake" BMC Pregnancy Childbirth 21(1):454 (2021)
https://bmcpregnancychildbirth.biomedce ... 21-03936-w
"Multivariate logistic regression analysis showed that multivitamin supplements containing iodine and milk consumption were risk factors for more than adequate iodine (UIC ≥ 250 μg/L). Iodine-rich diet was significantly related to heavier birthweight, larger head circumference and longer femur length of the newborns while more than adequate iodine intake (UIC ≥ 250 μg/L) was a risk factor for macrosomia."
Silva de Morais N, Ayres Saraiva D, Corcino C, Berbara T, Schtscherbyna A, Moreira K, Vaisman M, Alexander EK, Teixeira P - "Consequences of Iodine Deficiency and Excess in Pregnancy and Neonatal Outcomes: A Prospective Cohort Study in Rio de Janeiro, Brazil" Thyroid 30(12):1792-1801 (2020) doi: 10.1089/thy.2019.0462
https://www.liebertpub.com/doi/10.1089/thy.2019.0462
Xiao Y, Sun H, Li C, Li Y, Peng S, Fan C, Teng W, Shan Z - "Effect of Iodine Nutrition on Pregnancy Outcomes in an Iodine-Sufficient Area in China" Biol Trace Elem Res 182(2):231-237 (2018) doi: 10.1007/s12011-017-1101-4
https://pubmed.ncbi.nlm.nih.gov/28770411/
"In summary, during 1st trimester, both mild iodine deficiency and excessive iodine intake had adverse impacts on pregnancy outcomes in an iodine-sufficient area....more than adequate and excessive iodine was an independent risk factor for macrosomia (OR = 1.917, CI = 1.128–3.256, p = 0.016). "
Other:
SEE our literature list of over 300 studies discussed in our PFPC Members' forums, specifically as it applies to the more-than-adequate and excessive iodine consumption observed in the MIREC cohort:
The York/MIREC Studies - FAQ References
viewtopic.php?f=97&t=5022