I often see posts referring to heart problems and read that lack of proper thyroid treatment can affect the heart; here's a research paper....
"Evidence Analysis: The outcome of this analysis suggests that patients with untreated overt clinical or subclinical thyroid dysfunction are at increased risk of arrhythmia. Hyperthyroidism increased atrial arrhythmia; however, hypothyroidism increased ventricular arrhythmia."
"Conclusion: The early recognition and effective treatment of thyroid dysfunction in patients with arrhythmia is mandatory because the long-term prognosis of arrhythmia may be improved with the appropriate treatment of thyroid dysfunction".
Herz. 2015 Apr;40 Suppl 2:101-9. doi: 10.1007/s00059-014-4123-0. Epub 2014 Jul 4.
Arrhythmia and thyroid dysfunction.
Marrakchi S1, Kanoun F, Idriss S, Kammoun I, Kachboura S.
Picture from Wikipedia: "SinusRhythmLabels" by Created by Agateller (Anthony Atkielski)