Thyroid diseases, such as thyrotoxicosis, may exacerbate Pulmonary hypertension and are common in idiopathic pulmonary arterial hypertension. Evaluation of thyroid function is necessary to assess as symptom improvement has occurred after thyroid function has been restored. Serological testing may also detect the presence of a mixed connective tissue disorder, such as scleroderma or systemic lupus erythematosus.