One of the first things too look at, and not mentioned in your question, is the level of serum phosphorous. PTH levels rise when serum phosphorous levels rise. Lowering phosphorous can lower your PTH level, such that you may require less supplemental vitamin D if the serum phosphorous were between 3.5-5.5 meq/L.
If the phosphorous is within the target range, we would turn our attention to vitamin D levels (both 25 and 1,25). It's somewhat less likely that the levels of 1,25 di-hydroxy vitamin D in a CKD stage 4 patient would be normal. It is likely that your patient will have lower levels of the activated form of vitamin D and will require supplementation.
However, what if the activated vitamin D levels were normal? One would then have to reevaluate the stimuli for release of PTH. Briefly, those would be:
1) increased phosphorous level
2) unregulated release of PTH (that is, primary or tertiary hyperparathyroidism).
Tertiary hyperparathyroidism is more commonly seen in long-standing dialysis patients because they must have long-standing secondary hyperparathyroidism to develop this entity.
Primary hyperparathyroidism is also possible, though a little less likely with a normal calcium level. If you are entertaining this entity, I would recommend checking a serum ionized calcium to be sure that the levels are within the normal range.
A great resource, with an excellent algorithm, can be found here: