Evaluation of serum vitamin D levels in elderly patients with subclinical hypothyroidism

Abstract

Article HistoryReceived 12 / 05 / 2014 Accepted 07 / 06 / 2014Increasing numbers of researches have indicated the relationship between serum vitamin D level and several autoimmune diseases, because it has important roles in immune regulation. However, the role of vitamin D in the etiopathogenesis of these diseases is not well understood. Similarly, the detailed mechanism of vitamin D action on thyroid hormone metabolism and autoimmune thyroid diseases is still poorly understood. It was recently reported that patients with autoimmune thyroid disease showed lower vitamin D levels. However, there are few studies dealing with vitamin D status in elderly patients with subclinical hypothyroidism. We therefore aimed to investigate vitamin D levels in elderly patients with subclinical hypothyroidism. In the present study, a total of 37 patients (>70 years old) with subclinical hypothyroidism and 40 healthy controls (>70 years old) were retrospectively analyzed. Serum levels of free triiodothyronine (fT3), free thyroxine (fT4) and thyroid-stimulating hormone (TSH) were analyzed by chemiluminescence immunoassay (Centaur XP, Siemens Healthcare Diagnostics Inc., Tarrytown, USA). Serum levels of 25-Hydroxy vitamin D (25-OH D) were measured by chemiluminescence immunoassay (DiaSorin, Liaison, Italy). Serum anti thyroid peroxidase (anti-TPO) and anti thyroglobulin (anti-TG) were measured using a solid-phase, enzyme-labeled, chemiluminenescent sequential immunometric assay (Immulite 2000 XPi, Siemens Healthcare Diagnostics Inc., Tarrytown, USA). There was no significant difference between groups in terms of age and gender distribution. Serum TSH, anti-TPO and anti-TG levels in elderly patients with subclinical hypothyroidism showed higher values than healthy controls as expected. Serum 25-OH D levels in elderly patients with subclinical hypothyroidism were lower than healthy controls (p<0.001). These data may suggest association between serum 25-OH D levels and subclinical hypothyroidism in elderly patients. Further studies are needed to determine whether vitamin D insufficiency is a casual factor in the etiopathogenesis of subclinical hypothyroidism in elderly patients or rather a consequence of the disease.

Vitamin D and thyroid disorders: a systematic review and Meta-analysis of observational studies

“…Among these, 9 studies were from Turkey [ 26 , 34 , 36 , 37 , 39 , 42 , 43 , 48 , 49 ], 3 each from Saudi Arabia [ 17 , 32 , 35 ], Poland [ 38 , 52 , 59 ], China [ 27 , 28 , 51 ] and Korea [ 54 , 55 , 58 ], 2 each from Egypt [ 50 , 60 ] and Italy [ 40 , 57 ] and one each from Belgium [ 25 ], Canada [ 33 ], Brazil [ 44 ], Japan [ 47 ], India [ 45 ], Sweden [ 46 ], Thailand [ 53 ], Greece, United States [ 56 ], and Ukraine [ 31 ]. Among the 35 studies, 29 recruited both genders [ 25 , 27 – 32 , 34 – 41 , 43 – 46 , 48 – 56 , 58 ], 4 only women [ 17 , 42 , 47 , 57 ], and 2 studies did not report the gender [ 26 , 33 ]. Eighteen studies mentioned BMI [ 27 , 28 , 30 , 31 , 33 , 35 , 36 , 40 , 45 , 47 , 50 – 53 , 55 – 58 ] and 26 studies pointed to the time of ...…”

“…Pursuant to subgroup analysis, vitamin D and hypothyroidism were associated only among studies recruiting both genders (WMD − 15.43 ng/dl; 95% CI, − 29.49 to − 1.37) and studies that included the non-Asian population (WMD − 14.31 ng/dl; 95% CI, − 26.53 to − 2.10) (Table 2 ). Keeping out a number of studies including Ucar et al [ 34 ] (WMD − 11.33 ng/dl; 95% CI, − 22.76 to 0.08), Mackawy et al [ 32 ] (WMD − 11.40 ng/dl; 95% CI, − 22.92 to 0.10), Mirhosseini et al [ 33 ] (WMD − 14.41 ng/dl; 95% CI, − 29.01 to 0.18), Fawzy et al (a) [ 29 ] (WMD − 11.98 ng/dl; 95% CI, − 24.84 to 0.86) and Fawzy et al (b) [ 29 ] (WMD − 11.10 ng/dl; 95% CI, − 22.33 to 0.13) modified the overall effect. Due to evidence of publication bias (Begg’s test: P = 0.835, Egger’s test: P = 0.006), possible un-detected studies were tracked by trim and fill analysis, but this method could not add any dataset to our included ones.…”

“…Also, seasonal variation in serum vitamin D should be kept in mind when interpreting the results [ 64 ]. This fact has been excused in some papers [ 25 , 26 , 31 , 34 , 35 , 37 , 46 , 48 , 50 , 56 ]. Inconsistencies in terms of the season of sample collection could also influence our final results.…”

“…Inconsistencies in terms of the season of sample collection could also influence our final results. Besides, it has been proven that the bioavailability of vitamin D diminishes among overweight/obese individuals [ 65 ]; however, most of the included articles disregarded BMI as a confounding factor and probable source of heterogeneity [ 17 , 18 , 25 , 26 , 29 , 32 , 34 , 37 – 39 , 41 – 44 , 46 , 48 , 49 , 54 ].…”

Relationship Between Vitamin D and Thyroid: An Enigma

“…Mackawy et al measured serum 25(OH)D levels in 30 hypothyroid patients and 30 healthy participants, discovering that hypothyroid patients had hypovitaminosis D with hypocalcemia, which was significantly associated with the degree and severity of hypothyroidism [ 94 ]. In a retrospective study done in Turkey, Ucar et al demonstrated that serum 25(OH)D levels in elderly patients with subclinical hypothyroidism were lower than in healthy controls [ 95 ]. Aljohani et al, in a cross-sectional case-control study, found an inverse association between vitamin D status and FT3 [ 96 ].…”