Heart rate variability in hypothyroid patients: A systematic review and meta-analysis

Abstract

Introduction Hypothyroidism may be associated with changes in the autonomic regulation of the cardiovascular system, which may have clinical implications. Objective To conduct a systematic review and meta-analysis on the impact of hypothyroidism on HRV. Materials and methods PubMed, Cochrane, Embase and Google Scholar were searched until 20 August 2021 for articles reporting HRV parameters in untreated hypothyroidism and healthy controls. Random-effects meta-analysis were stratified by degree of hypothyroidism for each HRV parameters: RR intervals (or normal to normal-NN intervals), SDNN (standard deviation of RR intervals), RMSSD (square root of the mean difference of successive RR intervals), pNN50 (percentage of RR intervals with >50ms variation), total power (TP), LFnu (low-frequency normalized unit), HFnu (high-frequency), VLF (very low frequency), and LF/HF ratio. Results We included 17 studies with 11438 patients: 1163 hypothyroid patients and 10275 healthy controls. There was a decrease in SDNN (effect size = -1.27, 95% CI -1.72 to -0.83), RMSSD (-1.66, -2.32 to -1.00), pNN50 (-1.41, -1.98 to -0.84), TP (-1.55, -2.1 to -1.00), HFnu (-1.21, -1.78 to -0.63) with an increase in LFnu (1.14, 0.63 to 1.66) and LF/HF ratio (1.26, 0.71 to 1.81) (p <0.001). 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. The increased sympathetic and decreased parasympathetic activity may have clinical implications.

Effect of the Marine Exercise Retreat Program on Thyroid-Related Hormones in Middle-Aged Euthyroid Women

“…As the nLF and LF/HF ratios are indicators of the relative level of sympathetic activity compared with parasympathetic activity, the SNS is activated more than PNS as the TSH level goes to both ends of the euthyroid TSH range. Brusseau et al [ 51 , 52 ] reported that the nLF and LF/HF ratio increased in hyperthyroid patients with decreased TSH levels, while the nLF and LF/HF ratio increased in hypothyroid patients with increased TSH levels. Although the results of the study did not enlist euthyroid patients, they are consistent with the opposite trend in the nLF and LF/HF ratio in the high and low TSH groups.…”

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“…в группе пациентов с манифестным гипотиреозом меньший процент пациентов с показателем ци<1,24, по-видимому, обусловлен чрезмерной активностью парасимпатической нервной системы, что также определяет высокий риск сердечно-сосудистых событий. необходимо отметить, что процент случаев показателя ци<1,24 у пациентов в группе субклинического гипотиреоза и группе контроля значимо не отличался [21][22][23].…”

“…в исследованиях показано, что пациенты с импSt с самыми низкими значениями SDnn, свидетельствующими о выраженной активации симпатической нервной системы, имели повышенный риск смерти от всех причин и смертности от сердечно-сосудистых заболеваний. однако, как известно, клинические признаки гипотиреоза предполагают гипоактивность симпатической и активацию парасимпатической нервной системы, которая характеризуется снижением частоты сердечных сокращений, снижением сердечного выброса и сократимости сердца, а также возникновением желудочковых нарушений ритма [22]. в литературе нет однозначного мнения о преобладании активности симпатической или парасимпатической звеньев внс при данной сочетанной патологии.…”

A gene network implicated in the joint-muscle pain, brain fog, chronic fatigue, and bowel irregularity of Ehlers-Danlos and “long” COVID19 syndromes

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