https://next.amboss.com/us/article/UI0bXh?utm_source=navbar&utm_medium=anki&utm_campaign=anki&utm_term=pthrp&guid=G%2528w%257D5%252Cp1%257D%2560&aid=5a07b808-586d-41e2-a011-91a78f9e7acc&uid=2DSgTdbEa#Zfaaf49ccb69fcd674c3c095c9e6d59d2
AMBOSS lists other causes of HHoM (link here: https://next.amboss.com/us/article/lk0vLT?utm_source=navbar&utm_medium=anki&utm_campaign=anki&utm_term=pthrp&guid=G%2528w%257D5%252Cp1%257D%2560&aid=5a07b808-586d-41e2-a011-91a78f9e7acc&uid=2DSgTdbEa#Zf0284e0104fd9c2e96e312f795d8720c)
But it notes that PTHrP is the most common cause
Source: AMBOSS - https://next.amboss.com/us/article/UI0bXh?utm_source=navbar&utm_medium=anki&utm_campaign=anki&utm_term=pthrp&guid=G%2528w%257D5%252Cp1%257D%2560&aid=5a07b808-586d-41e2-a011-91a78f9e7acc&uid=2DSgTdbEa#Zfaaf49ccb69fcd674c3c095c9e6d59d2