TG and hypothyroidism: Background: Heart rate variability (HRV) reflects the balance between the sympathetic and parasympathetic divisions of the autonomic nervous system. Anti-thyroid antibodies like anti-TPO and anti-Thyroglobulin have long been associated with thyroid dysfunction and abnormal thyroid profile testing. Subclinical hypothyroidism (SCHypo) is characterized by elevated thyroid-stimulating hormone (TSH) with normal thyroid hormones. We hypothesize that autonomic function may be deranged in anti-TPO positive sub-clinical hypothyroid cases, even before the onset of overt hypothyroidism.