Hyperthyroidism and glucose intolerance

Two Cases of Thyrotoxicosis and Euglycemic Diabetic Ketoacidosis Under Sodium-glucose Transport Protein 2 Inhibitor Treatment

Thyrotoxicosis and sodium-glucose transport protein 2 inhibitors (SGLT2is) are associated with the induction of euglycemic diabetic ketoacidosis (euDKA). We herein report two cases of euDKA in patients with diabetes mellitus wherein both thyrotoxicosis and SGLT2i treatment were the underlying causes. One patient developed thyrotoxicosis during the course of type 2 diabetes mellitus, whereas the other patient was suspected of developing slowly progressive insulin-dependent diabetes mellitus during the course of Graves' disease. Although such cases are rare, there is some concern that similar cases may occur because of the increased frequency of SGLT2i use in recent years.

Glycemic variation in uncontrolled Graves' disease patients with normal glucose metabolism: Assessment by continuous glucose monitoring

PURPOSE

To observe the glycemic variation (GV) in uncontrolled Graves' disease (GD) patients with normal glucose metabolism measured by continuous glucose monitoring (CGM).

METHODS

This was a single-center, open-label, observational study. From January 2017 to October 2017, 20 GD patients with normal glucose metabolism and 24 healthy control subjects were recruited. Serum samples were obtained at 0, 30, and 120 min after oral glucose loading for glucose, insulin, and C-peptide level measurements. Fasting plasma fasting free triiodothyronine (FT3), free thyroxin (FT4), and thyroid stimulating hormone concentrations were also detected. All participants were subjected to a 3-day CGM after baseline data were collected. The primary endpoint was the difference in the mean amplitude of the glycemic excursions between the two groups.

RESULTS

Compared with the healthy subjects, the GD patients had higher mean amplitude of glycemic excursions (MAGE) (P < 0.01). Multiple linear stepwise regression analysis showed that FT4 level was an independent factor for the MAGE. Interestingly, the GD patients had a significant prolongation in the time to peak glucose, especially after breakfast (P < 0.01), and the elevation in the incremental area under the curve of glucose after breakfast till 4 hours later.

CONCLUSIONS

Uncontrolled GD patients with normal glucose metabolism had a greater GV, and the FT4 level may contributed to the increased GV.

Yangxin Tongmai Formula ameliorates impaired glucose tolerance in children with Graves' disease through upregulation of the insulin receptor levels

Graves' disease (GD) is the leading cause of hyperthyroidism, and the majority of GD patients eventually develop disorders of glucose handling, which further affects their quality of life. Yangxin Tongmai formula (YTF) is modified from a famous formula of traditional Chinese medicine for the treatment of cardiovascular diseases. In this study we investigated the potential effects of YTF in the treatment of pediatric GD patients with impaired glucose tolerance. Forty pediatric GD patients and 20 healthy children were recruited for this clinical study. Based on the glucose tolerance, the GD patients were divided into two groups: 20 patients displayed impaired glucose tolerance, while the other 20 patients displayed normal glucose tolerance. YTF was orally administered for 60 days. YTF administration significantly ameliorated the abnormal glucose tolerance and insulin sensitivity in the GD patients with impaired glucose tolerance. To determine the molecular mechanisms of this observation, the number of plasma insulin receptors was determined by ELISA. Before treatment, the fasting and postprandial levels of the insulin receptor were significantly lower in patients with impaired glucose tolerance compared with those in patients with normal glucose tolerance and healthy children. After YTF treatment, both the fasting and the postprandial circulating insulin receptor levels were upregulated, and close to those in healthy children. Therefore, YTF is a potential effective treatment to enhance glucose handling in GD children with impaired glucose tolerance.

Glucose metabolism before and after radioiodine therapy of a patient with Graves' disease: Assessment by continuous glucose monitoring

Hyperthyroidism causes impaired glucose tolerance, insulin resistance (IR) and insulin secretion. However, the glucose variability affected by thyroid dysfunction remains unclear. Glucose variability was assessed by continuous glucose monitoring (CGM) in a non-diabetic patient with Graves' disease (GD), to the best of our knowledge, for the first time. A 28-year-old man with GD, who had been taking methimazole for 4 years, was treated with radioiodine on August 17th 2016. Although the patient exhibited normal glycated hemoglobin (HbA1c; 5.3%) and blood glucose values during the oral glucose tolerance test (OGTT; fasting and 120 min blood glucose were 5.38 and 6.39 mmol/l, respectively) before radioiodine therapy, CGM exhibited high 24 h mean glucose and nocturnal hyperglycemia. An increased fasting insulin level, suppressed levels of blood glucagon and high homeostatic model assessment of IR were also observed. The disordered glucose metabolism improved as soon as the patient's thyroid function turned to hypothyroidism 4 months after radioiodine therapy. The glucose intolerance in patients with hyperthyroidism, missed by the OGTT and HbA1c tests, may be more common than anticipated.

Hypothyroidism in rats decreases peripheral glucose utilisation, a defect partially corrected by central leptin infusion

AIMS/HYPOTHESIS

The aims of this work were to determine the effect of hypothyroidism on insulin-stimulated glucose turnover and to unravel the potential mechanisms involved in such an effect.

METHODS

Hypothyroidism was induced by administration of propylthiouracil, with partial T4 substitution. Euglycaemic-hyperinsulinaemic clamps, associated with the labelled 2-deoxy-D-glucose technique for measuring tissue-specific glucose utilisation, were used. To assess a possible involvement of leptin in the modulation of glucose metabolism by hypothyroidism, leptin was infused intracerebroventricularly for 6 days. A group of leptin-infused rats was treated with rT3 to determine a potential role of T3 in mediating the leptin effects.

RESULTS

Compared with euthyroid rats, hypothyroid animals exhibited decreased overall glucose turnover and decreased glucose utilisation indices in skeletal muscle and adipose tissue. Leptinaemia in hypothyroid rats was lower while resistin mRNA expression in adipose tissue was higher than in euthyroid animals. Intracerebroventricular leptin infusion in hypothyroid rats partially restored overall, muscle and adipose tissue insulin-stimulated glucose utilisation and improved the reduced glycaemic response observed during insulin tolerance tests. The leptin effects were due neither to the observed increase in plasma T3 levels nor to changes in the high adipose tissue resistin expression of hypothyroid rats. The administration of leptin to hypothyroid animals was accompanied by increased expression of muscle and adipose tissue carnitine palmitoyl transferases, decreased plasma NEFA levels and reduced muscle triglyceride content.

CONCLUSIONS/INTERPRETATION

Hypothyroidism is characterised by decreased insulin responsiveness, partly mediated by an exaggerated glucose-fatty acid cycle that is partly alleviated by intracerebroventricular leptin administration.

Early changes in plasma glucagon and growth hormone response to oral glucose in experimental hyperthyroidism

The mechanisms underlying deterioration of glucose tolerance associated with hyperthyroidism are not completely understood. Increases in glucagon and growth hormone (GH) secretion have been previously found in hyperthyroid subjects, and could play a crucial role in this phenomenon. However, studies have not yet established the time sequence of changes in plasma glucose on the one hand and glucagon and GH on the other. To assess the early effects of thyroid hormone excess on glucose tolerance and plasma concentrations of the main glucoregulatory hormones, 12 nondiabetic euthyroid subjects underwent an oral glucose tolerance test (OGTT) before and after triiodothyronine ([T3] 120 micrograms/d) was administered for 10 days. Plasma levels of glucose, insulin, glucagon, and GH were determined at fasting and after the glucose load. T3 administration caused a marked increase in serum T3 (8.8 +/- 0.6 v 2.0 +/- 0.1 nmol/L), with clinical and biochemical signs of thyrotoxicosis. During the treatment, plasma glucose significantly increased both at fasting and after the glucose load (basal, 5.3 +/- 0.1 v 4.9 +/- 0.2 mmol/L, P < .05; area under the curve [AUC] for OGTT, 7.7 +/- 0.3 v 6.7 +/- 0.4 mmol/L min, P < .01) without any change in plasma insulin levels. After T3 administration, plasma glucagon levels were lower than at baseline (basal, 92 +/- 7 v 148 +/- 35 ng/L; AUC, 74 +/- 6 v 98 +/- 16 ng/L.min, P < .05), showing an appropriate reduction by the increased glucose levels. Conversely, plasma GH showed impaired suppression by hyperglycemia (AUC, 1.2 +/- 0.3 v 0.7 +/- 0.2 microgram/L.min, P < .05). In conclusion, thyroid hormone excess rapidly impairs glucose tolerance. Altered secretion of GH is an early event in thyrotoxicosis accompanying the onset of hyperglycemia, whereas plasma glucagon is appropriately suppressed by the increased plasma glucose levels. Thus, GH but not glucagon may contribute to the early hyperglycemic effect of thyrotoxicosis.

Glucose intolerance in chronic respiratory failure

A 75-g oral glucose tolerance test (OGTT) was performed on 18 patients with chronic respiratory failure and without fasting hyperglycemia, positive urine glucose, or hepatic/pancreatic disorders. Underlying diseases in these patients were pulmonary emphysema (11 cases, 61%), pulmonary tuberculosis (5 cases, 28%), and chronic bronchial asthma (2 cases, 11%). The body mass index (mean +/- SD, 17.6 +/- 2.2 kg/m2, P < 0.001) in these patients was significantly lower than that (23.8 +/- 3.1 kg/m2) in normal subjects. The OGTT results showed an impaired glucose tolerance pattern in 9 cases (50%) and a diabetes mellitus pattern in 6 cases (34%). The mean two-hour plasma glucose value in the patients was 9.8 mmol/L. However, insulin secretion responded well to glucose loading. These results suggest that a high proportion of chronic respiratory failure patients may have an intolerance for glucose loading but a normal insulin secretion pattern.