My nail symptoms with hypothyroidism are onycholysis (separation of the nail from the nail bed) and peeling nails. When I was a teenager my sister used to say that I was using a pin to scrape under my nails to make them look longer lol. I only have onycholysis very mildly on my ring fingers now.
I don't have any moons either except my thumbs. I don't recall ever having moons so it's probably just my normal. I found this info about absent lunula...
"LUNULA:
missing (= absent nail moon)
IMPORTANT: An absent lunula is perfectly natural on the little finger!
Many people have 8 lunula, though some of them might be hidden under the cuticles - because the lunula are typically diminishing in size from the thumb to the little finger. Fewer than 8 lunula can signal various vulnerabilities such as: malnutrition, protein deficiency, vitamin A deficiency, anemia (deficiency of red blood cells), not enough oxygenation, poor circulation, numbness, or heart disease [source: Medscape]. No lunula at all on all fingers (missing lunula) has been recognized as a feature of various chromosome abnormalities." - Absent lunula - Hand Research.
"Small or No Moons: There is very little research on this topic; however, one study has shown that missing moons are associated with various systemic disorders including issues with your thyroid or pituitary gland, iron deficiency, chronic renal failure, depression and possible B-12 deficiency." - This Green Earth - Low Energy? Look At Your Fingernail Moons
Red_Star,
I don't know if we can just assume that missing lunula is normal. For example, in my case, I have had lethargy, fatigue symptoms much before my hypothyroid was diagnosed. Probably, there is an interplay between deficiency and thyroid, probably there is an association, deficiency maybe a causal factor also. We don't know that.
Unfortunately, even in yearly health check ups, standard procedure is to check your regular blood work, BP, Sugar, Eyes, Heart etc. and no one really cares about deficiencies in standard health check ups. In fact, I had to request my Doctor to add Creatinine test to the list.
On my part, I have always accepted that it is my body nature that makes me lethargic and sluggish. Had I told Doctor that I don't feel all that active, they would have probably tested for deficiencies.
We normally take it as an issue only when we feel pain and everything else is assumed to be part of aging or body nature. For example, I complained only when I had body aches after which Doctor diagnosed me with Hypo.
Probably I had some level of Hypothyroid 1-2 years before that but being slow and sluggish was taken as a part of aging by me and only when it got down to pain, I thought of going to Doctor.