Baseline characteristics of the 356 PH patients, including age, sex, TSH levels, and WHO symptom class, stratified by WHO group, were compared with those of the 698 patients in the control group (Table 1
). The entire PH group and WHO group 1 patients were slightly younger. The control group of 698 patients had the same sex ratio as the entire PH group by design; however, the WHO group 1, particularly the IPAH group, had a higher percentage of female patients. The combined WHO groups 2, 3, and 4 had a lower percentage of female patients than the control patients. Compared with the control patients, PH patients had higher TSH values. The conditions for which the patients in the control group were evaluated in the pulmonary clinic were classified into the following arbitrary groups: obstructive lung disease, n = 190 (27%); chronic cough, n = 120 (17%); undifferentiated dyspnea, n = 115 (17%); abnormal radiographic findings, n = 88 (13%); lung cancer, n = 45 (6%); bronchiectasis, including atypical mycobacterial disease, n = 26 (4%); and interstitial lung disease, n = 24 (3%). The remaining 90 patients (13%) had miscellaneous conditions, including chest pain, hemoptysis, pulmonary embolism, sarcoidosis, pleural disease, sleep disorders, and neuromuscular weakness.