Thyroid function and anti-thyroid antibodies in Iranian patients with type 1 diabetes mellitus: influences of age and sex

Type 1 diabetes mellitus is frequently associated with autoimmune thyroid disease [ATD].Genetic susceptibility for autoantibody formation in association with ATD and type 1 diabetes mellitus has been described with varying frequencies, but there is still debate about its prevailing situation in Iran. We have therefore investigated the prevalence of anti-thyroid peroxidase [anti-TPO] and anti thyroglubolin [Anti TG] antibodies in type 1 diabetic patients, and compared the effect of age and sex on the thyroid autoimmunity in patients with type 1 diabetes mellitus in Iran. Ninety one subjects with type 1 diabetes mellitus and one hundred and sixty three unrelated normal controls under the age of thirty years were recruited for the detection of anti-TPO and anti-TG. Radio Immuno Assay and chemiluminescence methods were used for anti-TPO and anti-TG detection respectively. Among 91 type 1 diabetic patients, 36 [39.6%] were positive for anti-TPO and 27[30%] were positive for antiTG. Anti-TPO antibodies were detected only in 6.7% of control group. Comparing with those without thyroid autoimmunity, there was a female preponderance for the type 1 diabetic patients with thyroid autoimmunity [female: male, 28:14 vs. 28:20 respectively]. Among the type 1 diabetic patients those with thyroid autoimmunity, tended to be older [p: 0.04] and to have higher TSH concentration [p: 0.03]. Patients with high anti-TPO levels had longer duration of diabetes [P: 0.02]. The presence of anti-TPO in 39.6% of our type 1 diabetic patients comparing with 8.5% of normal subjects confirmed the strong association of ATD and type 1 diabetes mellitus

Autoradiographic thyroid evaluation in short-term experimental diabetes mellitus

Previous studies have shown that in vitro thyroid peroxidase (TPO) iodide oxidation activity is decreased and thyroid T4-5' -deiodinase activity is increased 15 days after induction of experimental diabetes mellitus (DM). In the present study we used thyroid histoautoradiography, an indirect assay of in vivo TPO activity, to determine the possible parallelism between the in vitro and in vivo changes induced by experimental DM. DM was induced in male Wistar rats (about 250 g body weight) by a single ip streptozotocin injection (45 mg/kg), while control c animals received a single injection of the vehicle. Seven and 30 days after diabetes induction, each diabetic and control animal was given ip a tracer dose of I (2 muCi), 2.5 h before thyroid excision. The glands were counted, weighed, fixed in Bouin's solution, embedded in paraffin and cut. The sections were stained with HE and exposed to NTB-2 emulsion (Kodak). The autohistograms were developed and the quantitative distribution of silver grains was evaluated with a computerized image analyzer system. Thyroid radioiodine uptake was significantly decreased only after 30 days of DM (C:0.38 + 0.05 vs DM: 0.20 + 0.04 percent/mg thyroid, P<0.05) while in vivo TPO activity was significantly decreased 7 and 30 days after DM induction (C:5.3 and 4.5 grains/100 mum2 vs DM: 2.9 and 1.6 grains/100 mum2, respectively, P<0.05). These data suggest that insulin deficiency first reduces in vivo TPO activity during short-term experimental diabetes mellitus.

Effects of estradiol benzoate on 5'-iodothyronine deiodinase activities in female rat anterior pituitary gland, liver and thyroid gland

There is little information on the possible effects of estrogen on the activity of 5'-deiodinase (5'-ID), an enzyme responsible for the generation of T3, the biologically active thyroid hormone. In the present study, anterior pituitary sonicates or hepatic and thyroid microsomes from ovariectomized (OVX) rats treated or not with estradiol benzoate (EB, 0.7 or 14 mug/100 g body weight, sc, for 10 days) were assayed for type I 5'-ID (5'-ID-I) and type II 5'-ID (5'-ID-II, only in pituitary) activities. The 5'-ID activity was evaluated by the release of (125)I from deiodinated (125)I rT3, using specific assay conditions for type I or type II. Serum TSH and free T3 and free T4 were measured by radioimmunoassay. OVX alone induced a reduction in pituitary 5'-ID-I (control = 723.7 + 67.9 vs OVX = 413.9 + 26.9; P<0.05), while the EB-treated OVX group showed activity similar to that of the normal group. Thyroid 5'-ID-I showed the same pattern of changes, but these changes were not statistically significant. Pituitary and hepatic 5'-ID-II did not show major alterations. The treatment with the higher EB dose (14 mug), contrary to the results obtained with the lower dose, had no effect on the reduced pituitary 5'-ID-I of OVX rats. However, it induced an imporatnt increment of 5'-ID-I in the thyroid gland (0.8 times higher than that of the normal group: control = 131.9 + 23.7 vs OVX + EB 14 mug = 248.0 + 31.2; P<0.05), which is associated with increased serum TSH (0.6-fold vs OVX, P<0.05) but normal serum free T3 and free T4. The data suggest that estrogen is a physiological stimulator of anterior pituitary 5'-ID-I and a potent stimulator of the thyroid enzyme when employed at high doses.