IRCT20211026052878N1 IRCT 2021-12-18 Tehran University of Medical Sciences The effect of vitamin D on recurrence of chronic rhinosinusitis associated with nasal polyposis Evaluation of the effect of vitamin D on recurrence of chronic rhinosinusitis associated with nasal polyposis after functional endoscopic sinus surgery (Triple blind, Placebo-controlled randomized clinical trial) 2021-12-11 anticipated 100 Complete https://irct.ir/trial/59878 interventional Randomization: Randomized, Blinding: Triple blinded, Placebo: Used, Assignment: Parallel, Purpose: Prevention, Randomization description: Blocked Randomization is used. Four blocks of defined intervention (A) and control (B) groups (AABB, ABAB, ABBA, BBAA, BABA, BAAB) and written on cards 1-6, the cards are placed in the envelope. The cards are then randomly selected and a random string is made from the selected card sequence. Patients in the intervention and control groups are included in the study based on this sequence, Blinding description: Participants, the surgeon, the statistician who analyzes the study are kept blind to their assignment to study groups. 3 Chronic rhinosinusitis with nasal polyposis. Intervention 1: Intervention group: Patients with chronic rhinosinusitis associated with polyposis treated with vitamin D. Both control and intervention groups will be divided into three subgroups. The first subgroup has a vitamin D level below 20 ng / ml (deficient), the second subgroup has a vitamin D level of 20-29 ng / ml (Insufficient), the third subgroup has a vitamin D level greater than 30 ng / ml (Sufficient).The first subgroup receives 50,000 units of vitamin D eight weeks weekly and then monthly. The second subgroup receives 50,000 units of vitamin D eight weeks weekly and then monthly. The third subgroup receives 50,000 units of vitamin D per month. Intervention 2: Control group: Patients with chronic rhinosinusitis associated with polyposis treated with placebo in a similar way. Undecided - It is not yet known if there will be a plan to make this available Justification or reason for indecision in sharing IPD is There is no more information.