What Causes Calcified Lung Nodules?

Question: Hello, My 51 yr old non smoking non drinking , husband has CT finding of 4mm non calcified lung nodule when looking at abdominal cte for anemia(mild) (has had mild anemia 4 years. )and many pos FOB test so after all scopes normal CTE was done to investigate. Physical findings for yearly exam. No lung illness that I can recall in . Out of country travel up to 1- 3 weeks only at a time is 1-2 times yearly to Asia and Europe. From USA. We do not live in any "valley fever" area.
The lower lung portion was incidental on CT for abdomen and they report this nodule and to get CT of lungs now to look for more nodules.
I had film of same area on CT from 2011 (disc copy) and nodule was not present in that abdominal CT. nor mentioned in report. Nor was the assumed Crohns suggestive findings of recent. (looking for FOB reason)
Main reason to write is this question: Would the absence of the nodule in 2011 suggest the nodule is growing or do they start out 4mm ? is more aggressive better to look at this or wait and see as I feel the doctor will say to do. If other nodules are found what is that reason?
It is in lower lobe Right lung not at wall but close to it than not.
He has bit of dry cough occasionally daily for several month as if something small in throat (a tickle) or such, 60 lb weight loss in last 4 years --claims he dieted-He now weighs 2oo plus at 6 ft tall.
He also has some worsening mild shaking in hands not unlike Parkinson's . Thank you and have a pleasant day.

Thank you so much.
I am glad to hear the idea of Crhons maybe cause of lung nodule. That had not been suggested to us.
I will tell his doctor the idea.
His doctor is from XXXXXXX and very kind and takes time to talk to me and call.
He will be open to ideas from others.
I felt your answer was good. and for $35 much easier than a consult locally and an appointment extra for this one question regarding size growth.
have nice day. धन्यवाद्