A significant proportion of patients with hyperthyroidism may have mild pulmonary hypertension (PH), according to the results of a recent study. Increased pulmonary vascular resistance may be the underlying cause of this association.
Hyperthyroidism is a set of disorders that involve the excessive production and release of thyroid hormones (TSH) by the thyroid gland. This condition has a significant impact on the cardiovascular system and is associated with a large number of cardiovascular manifestations, including increased blood pressure and heart failure. The most common causes of hyperthyroidism are Graves’ disease and toxic multinodular goiter.
“Recent studies have demonstrated a high prevalence of [pulmonary hypertension] in patients with hyperthyroidism, and the reversal of [pulmonary hypertension] after successful treatment to achieve a euthyroid state [normal thyroid function],” researchers wrote. “In observational studies, the prevalence of [pulmonary hypertension] in patients with hyperthyroidism was shown to vary between 35% and 47%.”
However, the disease mechanisms for the development of pulmonary hypertension in patients with hyperthyroidism have not been completely understood, they wrote.
The study enrolled 129 patients with hyperthyroidism, 37 with hypothyroidism, and 38 euthyroid controls. Researchers investigated the association between PH and several parameters, including blood levels of TSH receptor antibodies (TRAb), thyroid peroxidase antibody, thyroglobulin antibody, TSH, free triiodothyronine (fT3), fT4 levels, and dyspnea (shortness of breath) during daily activities.
Results showed that mild PH was detected in 35% of patients with Graves’ disease, 36% of patients with toxic multinodular goiter, 13.5% of patients with hypothyroidism, and 5% of euthyroid controls.
Pulmonary vascular resistance (PVR) was increased in hyperthyroid patients with pulmonary hypertension compared to patients without it. No association was reported between PH and blood levels of the TSH receptor antibody, thyroid peroxidase antibody, thyroglobulin antibody, TSH, fT3 and fT4 levels.
“Mild [pulmonary hypertension] is present in a significant proportion of patients with hyperthyroidism, regardless of [its cause],” researchers concluded. “PVR appears to be the main cause of [pulmonary hypertension] in patients with hyperthyroidism, and neither autoimmunity nor thyroid hormones are associated with [pulmonary hypertension] in these patients. Mild dyspnea during daily activities in patients with hyperthyroidism may be related to [pulmonary hypertension]; however, severe dyspnea requires further evaluation.”