What used to be called hypochondriacis, we now know can be any number of identifiable disorders.
Some people are clinically depressed and genuinely feel pain. It has been known for many years that there was a Depression/pain/slash/depression cycle; that pain and some forms of depression go hand and hand. The cause of this kind of pain may not show up on an X-ray or MRI but it is very real, nonetheless.
Chronic fatigue and fibro-myalgia are very real, in that the person is genuinely exhausted beyond all reason and/or is a big ball of pain. One day, some very smart people will figure out what's really going on chemically with these diseases. (dis-ease). In the meanwhile, there are drugs that help a great many people, though not all.
Chronic pain can depress and exhaust the strongest among us.
Many of the new syndromes and such are highly stress related. Of course, just about everything is stress related, from stomach ulcers to cancer.
The best way to know how to deal with someone who, at least in your estimation, shows signs of hypochondria is to find out what's really going on.