Diastolic Hypertension in Hypothyroidism: Mechanism

Hypothyroidism has been recognized as a cause of secondary hypertension.

Previous studies on the prevalence of hypertension in subjects with hypothyroidism have demonstrated elevated diastolic blood pressure values. (hypertension in ~30% of patients)

WHY???

In hypothyroidism, there is endothelial dysfunction and arterial smooth muscle compliance is reduced => leads to increased Systemic Vascular Resistance (SVR).

This appears to be a multi-factorial mechanism (increased adrenergic activity and reduction in endothelial-derived relaxation factor (EDRF) availability). 

REFERENCES

1. Klein, I and Danzi, S. Thyroid Disease and the Heart. Circulation. 2007;116:1725-1735.
2. Klein I, Ojamaa K. Thyroid hormone and the cardiovascular system. N Engl J Med. 2001;344(7):501.
3. Taddei S, Caraccio N, Virdis A, Dardano A, Versari D, Chiadoni L, Salvetti A, Ferrannini E, Monzani F. Impaired endothelium-dependent vasodilatation in subclinical hypothyroidism: beneficial effect of levothyroxine therapy. J Clin Endocrinol Metab. 2003; 88: 3731–3737.