Endocrine Abstracts

Introduction: Hypothyroidism is a clinical syndrome resulting from a deficiency of thyroid hormones, which in turn results in a generalized slowing down of metabolic processes. There are consistent reports demonstrating that many diseases, including the thyroid gland dysfunction are associated with changes of serum homocysteine (tHcy) level, with its genetic and epigenetic causes.

Case report: In 2018 we reported 51 and 52-year-old sisters diagnosed with subclinical and manifested hypothyroidism accordingly. One of them was enrolled to a research study related to the link between MTHFR gene polymorphisms, DNA methylation status and hypothyroidism (T. Kvaratskhelia et al.). Both siblings revealed MTHFR gene 677 TT genotype. We also investigated two other siblings from the same family without history of hypothiroidism: 54-year-old female and 47-year-old male who showed CC genotype and their 82-year-old mother with CT genotype and an episode of thyroid failure in the past. After 6 years we report 88-year-old mother who developed subclinical hypothyroidism soon after initial study and the results of hyperhomocysteinemia management with vitamin supplements in all effected family members.

Methods: MTHFR gene was investigated by the PCR-RELF method using HinfI (NEB Inc) enzyme. Levels of DNMT1-3a and DNMT1 were measured in nuclear extracts of PBMC (Abcam). Total serum homocysteine concentrations were also measured. DNA samples underwent bisulfite modification (Qiagen) and methylation levels of Alu and LINE-1 were examined by the combined bisulfite restriction analysis-interspersed repetitive sequences (COBRA-IRS). We have added vitamin B group supplements for hyperhomocysteinemia management.

Results: Family members with TT and CT genotype had elevated levels ofDNMT3a compared with CC genotype. There was no significant difference in DNMT1 levels. tHcy levels were significantly elevated in study subjects with TT genotypes and slightly elevated in the individual with CT genotype in initial measurement, which increased at the presentation of hypothyroidism. Hypermethylated loci (mCmC) at Alu elements were significantly lower and LINE-1 hypermethylated loci (mCmC) were also lower in TT and CT genotypes compared with CC family members. Hyperhomocysteinemia management with supplemets lead to the reduction of levothyroxine replacement doses in sisters, it improved thyroid function test results in mother who was not initiated levothyroxine replacement treatment and significantly improved dyslipidemia in all study subjects.

Conclusions: We smggest that molecular studies of MTHFR gene and its related epigenetic changes could be valuable for refining the clinical diagnosis of hypothyroidism, leading to its more precise management.