Effect of neonatal hypothyroidism on carbohydrate metabolism, insulin secretion, and pancreatic islets morphology of adult male offspring in rats

The Roles of Thyroid and Thyroid Hormone in Pancreas: Physiology and Pathology

It is widely accepted that thyroid hormones (THs), secreted from the thyroid, play important roles in energy metabolism. It is also known that THs also alter the functioning of other endocrine glands; however, their effects on pancreatic function have not yet been reviewed. One of the main functions of the pancreas is insulin secretion, which is altered in diabetes. Diabetes, therefore, could be related to thyroid dysfunction. Earlier research on this subject focused on TH regulation of pancreas function (such as insulin secretion) or on insulin function through TH-mediated increase of energy metabolism. Afterwards, epidemiological investigations and animal test research found a link between autoimmune diseases, thyroid dysfunction, and pancreas pathology; however, the underlying mechanisms remain unknown. Furthermore, recent studies have shown that THs also play important roles in pancreas development and on islet pathology, both in diabetes and in pancreatic cancer. Therefore, an overview of the effects of thyroid and THs on pancreas physiology and pathology is presented. The topics contained in this review include a summary of the relationship between autoimmune thyroid dysfunction and autoimmune pancreas lesions and the effects of THs on pancreas development and pancreas pathology (diabetes and pancreatic cancer).

The effect of maternal hypothyroidism on cardiac function and tolerance to ischemia-reperfusion injury in offspring male and female rats

PURPOSE

Accumulating evidence indicates that intrauterine evolution disturbance can contribute to myocardial ischemia reperfusion (IR) injury; in addition, thyroid hormones (THs) have a crucial role in the development of different systems during fetal life. The aim of this study was to determine the effect of TH deficiency during fetal life on tolerance of isolated heart to ischemia during adulthood in both genders.

METHODS

Hypothyroidism was induced in pregnant Wistar rats by administrating 0.025 % 6-propyl-2-thiouracil in drinking water throughout pregnancy. Offspring of rats with maternal hypothyroidism (MH) and control groups were tested in adulthood. Isolated hearts were perfused with Langendorff setup and exposed to 30 min of ischemia, followed by 45 min of reperfusion. Baseline values of the left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDP), heart rate (HR), and peak rates of positive and negative changes in left ventricular pressure (±dp/dt) were recorded.

RESULTS

In the MH groups the baseline levels of LVDP (male: 23 %, female: 33 %), HR (male: 31 %, female: 26 %), and ±dp/dt were significantly (p < 0.01) lower, compared to controls. After ischemia, hearts from male rats with MH had less tolerance to IR injury as assessed in terms of reductions in recovery of hemodynamic parameters compared to controls, while in female rats there were no significant differences between MH and controls.

CONCLUSIONS

MH decreases hemodynamic parameters in the heart of both male and female offspring in adulthood; in addition, hearts of male rats with MH show less tolerance to ischemia, compared to those of females.

Comparison of the effects of fetal hypothyroidism on glucose tolerance in male and female rat offspring

Thyroid hormones are vital for survival of mammalian species and play critical roles in growth, development, and metabolism. Both fetal hypothyroidism and sex can affect carbohydrate metabolism during adult life. This study aims to assess carbohydrate metabolism in male and female offspring born from mothers who were hypothyroid during pregnancy. Pregnant rats were divided into two groups; the controls consumed water and the hypothyroid group received water containing 0.025 % 6-propyl-2-thiouracial throughout gestation. The intravenous glucose tolerance test (0.5 g/kg glucose) was carried out in 3-month-old offspring. Findings showed that compared to controls, male fetal hypothyroid rats during adulthood had glucose intolerance (area under the curve: 446.4 ± 9.7 vs. 486.4 ± 8.8, p < 0.01 in control and fetal hypothyroid groups, respectively) whereas females had improved glucose tolerance (478.1 ± 7.0 vs. 455.9 ± 8.5, p < 0.01). In conclusion, sex could modulate the effects of fetal hypothyroidism on glucose tolerance in rats.