Background and Aims. Previous studies report the presence of cognitive impairment in patients with overt hypothyroidism. The thyroid hormones are essential for neurological and intellectual functions. Type 2 diabetes mellitus (T2DM) subjects are exposed to higher risk of cognitive function alteration compared to nondiabetic subjects. The aim of the present study was to analyze the cognitive function of T2DM subjects with overt hypothyroidism.
Materials and Methods. We performed an observational study between 2015-2017. A total of 12 patients (11 women and 1 men) with overt hypothyroidism and T2DM were recruited for this study. Their cognitive function was compared with that of subjects of a control group (16 patients - 12 women and 4 men with T2DM but without overt hypothyroidism). Cognitive function was evaluated using the Mini Mental State Examination (MMSE) test. Serum thyroid stimulating hormone (TSH) levels were measured by immunoradiometric assay, free thyroxine (FT4) by radioimmunoassay while fasting plasma glucose (FPG) levels were evaluated using automated devices.
Results. There were no significant differences between the two groups in respect of age and FPG. In the study group, mean TSH and FT4 levels were 11.76±4.43 mIU/L, resepectively 0.53±0.08 ng/dL while in the control group these were 2.60±0.40 mIU/L, respectively 1.12±0.19 ng/dL (p<0.001). Moderate cognitive impairment was present in 3 patients of the study group (25.00%) and in 2 subjects from the control group (12.50%). Mild cognitive impairment was present in 4 patients (33.33%) of the study group and in 2 subjects from the control group (12.50%).
Conclusion. This study showed that MMSE scores are significantly reduced in subjects with T2DM and hypothyroidism compared to subjects with T2DM without hypothyroidism (p<0.004). The study revealed a negative correlation between TSH and MMSE score in the study group.
1. Ceresini G, Lauretani F, Maggio M et al. Thyroid function abnormalities and cognitive impairment in elderly people: results of the Invecchiare in Chianti study. J Am Geriatr Soc 57: 89–93, 2009.
2. Correia N, Mullally S, Cooke G et al. Evidence for a specific defect in hippocampal memory in overt and subclinical hypothyroidism. J Clin Endocrinol Metab, 94: 3789–3797, 2009.
3. Quinlan P, Nordlund A, Lind K, Gustafson D, Edman A, Wallin A. Thyroid hormones are associated with poorer cognition in mild cognitive impairment. Dement Geriatr Cogn Disord 30: 205–211, 2010.
4. Gussekloo J, Van Exel E, De Craen AJ, Meinders AE, Frölich M, Westendorp RG. Thyroid status, disability and cognitive function, and survival in old age. JAMA 292: 2591–2599, 2004.
5. Gilbert ME, Sui L. Dose-dependent reductions in spatial learning and synaptic function in the dentate gyrus of adult rats following developmental thyroid hormone insufficiency. Brain Res 1069: 10–22, 2006.
6. Goldey ES, Kehn LS, Rehnberg GL, Crofton KM. Effects of developmental hypothyroidism on auditory and motor function in the rat. Toxicol Appl Pharmacol 135: 67–76, 1995.
7. Smith JW, Evans AT, Costall B, Smythe JW. Thyroid hormones, brain function and cognition: a brief review. Neurosci Biobehav Rev 26: 45–60, 2002.
8. Morreale de Escobar, G, Obregon MJ, del Rey FE. Maternal thyroid hormones early in pregnancy and fetal brain development. Best Pract Res Clin Endocrinol Metab 18: 225–248, 2004.
9. Zoeller RT, Rovet J. Timing of thyroid hormone action in the developing brain: clinical observations and experimental findings. J Neuroendocrinol 16: 809–818, 2004.
10. Hogervorst E, Huppert F, Matthews FE, Brayne C. Thyroid function and cognitive decline in the MRC funded cognitive function and ageing study. Psychoneuroendocrinology 33: 1013–1022, 2008.
11. van Boxtel MPJ, Menheere PPCA, Bekers O, Hogervorst E, Jolles J. Thyroid function, depressed mood, and cognitive performance in older individuals: the Maastricht aging study. Psychoneuroendocrinology 29: 891–898, 2004.
12. Umegaki H. Type 2 diabetes as a risk factor for cognitive impairment: current insights. Clin Interv Aging 9: 1011–1019, 2014.
13. Folstein MF, Folstein SE, McHugh PR. Mini-mental state. A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 12: 189–198, 1975.
14. Begin ME, Langlois MF, Lorrain D, Cunnane SC. Thyroid Function and cognition during aging. Curr Gerontol Geriatr Res 2008: 474868, 2008.
15. Osterweil D, Syndulko K, Cohen NS et al. Cognitive function in non-demented older adults with hypothyroidism. JAGS 40 :325-335,1992.
16. Bajaj S, Sachan S, Mirsa V, Varma A, Saxena P. Cognitive function in subclinical hypothyroidism in elderly. Indian J Endocrinol Metab 18(6): 811–814, 2014.
17. Wahlin Å, Wahlin T-BR, Small BJ, Bäckman L. Influences of thyroid stimulating hormone on cognitive functioning in very old age. Journals of Gerontology. Series B 53: P234–P239, 1998.
18. Jorde R, Waterloo K, Storhaug H, Nyrnes A, Sundsfjord J, Jenssen TG. Neuropsychological function and symptoms in subjects with subclinical hypothyroidism and the effect of thyroxine treatment. J Clin Endocrinol Metab 91: 145–153, 2006.