Association of vitamin D levels and receptor gene polymorphisms with medullary thyroid cancer

Thyroid cancer is the most common endocrine malignancy. Accounting for approximately 1-2% of all cancers. Thyroid cancers have been divided into four main types: papillary, follicular, medullary and anaplastic. The active form of vitamin D (1,25- (OH) 2-vitamin D3) by binding to its receptor, using genomic and non-genomic mechanisms inhibits the proliferative effect of TSH on thyroid cells. Therefore, vitamin D may have a role in regulating of thyroid gland cell proliferation. Many studies have shown anti-cancer effects of vitamin D in cancers. Polymorphisms of Vitamin D receptor can influence the prevalence to various cancers. In the present study, serum level of vitamin D and FokI, BsmI and Tru9I polymorphism of vitamin D receptor was investigated.
This case-control study was performed in the summer of 2015 in Endocrinology and Metabolism Center of Shahid Beheshti University of Medical Sciences, Tehran, Iran. Forty medullary thyroid cancer patients and 40 healthy controls were investigated. Genomic DNA of subjects was extracted with saturated salt/proteinase K and polymorphisms of vitamin D receptor gene investigated by polymerase chain reaction-sequencing. Serum level of vitamin D evaluated by ELISA technique. The results were analyzed by SPSS, ver. 20 (Chicago, IL, USA) and GraphPad Prism, ver. 5 (GraphPad, Inc., CA, USA) softwares.
Genotypic and allelic abundance of FokI and BsmI polymorphisms between test and control groups have not shown significant different. In Tru9I polymorphism, Tt genotype abundance in test group were 45 percent and in control group were 17.5 percent and t allelic abundance in test group were 25 percent and in control group were 8.7 percent which this different were significant. Average serum level of vitamin D in test group was 23.32 ng/ml and in control group was 18.95 ng/ml which was statistically significant.
Unexpectedly, serum levels of vitamin D in test group were higher than control group. Tru9I polymorphism is significantly correlated to medullary thyroid carcinoma prevalence.