Glucose variability before and after treatment of a patient with Graves' disease complicated by diabetes mellitus: assessment by continuous glucose monitoring

Thyroid Eye Disease and Its Association With Diabetes Mellitus: A Major Review

PURPOSE

Thyroid eye disease (TED) associated with diabetes mellitus (DM) presents unique challenges. DM is a risk factor for TED. Standard management of TED with glucocorticoids (GC), orbital radiation, or teprotumumab can cause adverse events in poor glycemic control. The authors reviewed the literature on the relationship between TED and DM and the management of co-existing diseases.

METHODS

The authors searched PubMed with keywords "thyroid eye disease," "diabetes mellitus," and similar terms from 2013 to 2022. The authors included relevant studies after screening the abstracts. Additional references to the selected studies were included where applicable. Data were extracted from the final articles according to the preplanned outline of the review.

RESULTS

The initial search yielded 279 abstracts. The final review included 93 articles. TED and DM interact at multiple levels-genetic, immunologic, cellular, nutritional, and metabolic. Both DM and thyroid dysfunction exacerbate the morbidity caused by the other. Metabolic factors also affect the inflammatory pathway for TED. Patients with DM develop TED with greater frequency and severity, necessitating interventions for vision salvage. Agents (GC, teprotumumab, or radiation) used for TED are often unsuitable for treatment with DM, especially if there is poor glycemic control or diabetic retinopathy. There were no studies on using steroid-sparing agents in TED with DM.

CONCLUSION

TED and DM co-exist because of multiple intersections in the pathophysiology. Challenges in the treatment include increased TED severity and risk of hyperglycemia and retinopathy. Multidisciplinary teams best undertake treatment of TED with DM.

Safety of Antithyroid Drugs in Avoiding Hyperglycemia or Hypoglycemia in Patients With Graves' Disease and Type 2 Diabetes Mellitus: A Literature Review

Graves' disease (GD) may increase the difficulty of glucose control in patients with type 2 diabetes mellitus (T2DM). Therefore, selecting a drug with limited blood glucose side effects is an important issue in patients with T2DM and GD. Antithyroid drugs (ATDs) including propylthiouracil (PTU), methimazole, and carbimazole are commonly prescribed for the treatment of GD. Here, we review and summarize the literature from the last 10 years and discuss the effects of current ATDs used for GD for blood glucose control in patients with T2DM. A search of the literature published between January 1, 2012 and December 1, 2022 was conducted using three major medical databases: Google Scholar, Ovid Medline, and Scopus. An initial search was conducted on PubMed using the MeSH terms "propylthiouracil," "methimazole," "carbimazole," and "hyperglycemia" or "hypoglycemia" in academic databases. All articles included "Graves' disease" and "type 2 diabetes mellitus" in the title. Based on the results of previous studies, the hyperglycemic and hypoglycemic side effects of ATDs can be explained by several possible mechanisms. The most widely accepted hypothesis is that sulfhydryl group drugs (e.g., methimazole and carbimazole) cleave the disulfide bond of insulin and enhance its immunogenicity, resulting in hypoglycemia. Moreover, some reports have indicated that methimazole is associated with hypoglycemia; therefore, if the patient has a history of autoimmune diseases, it is necessary to consider whether to change drugs or actively track the production of autoimmune antibodies. In non-diabetic and diabetic patients with GD, the hyperglycemic and hypoglycemic side effects of PTU (on glycemic variation) were less than that of thiamazole. However, as relatively few reports have investigated the side effects of blood sugar changes, further research is necessary to confirm these effects. In addition to autoimmune diseases, drug side effects may need to be considered. These findings provide considerations for clinicians to select more appropriate ATDs for patients with GD and T2DM, and implement improved care guidelines.

Changes in Glucose Intolerance after Treatment with Antithyroid Drugs in Patients with Graves' Disease Using Continuous Glucose Monitoring: A Pilot Study

Objective Graves' disease (GD) is known to cause glucose intolerance. The present study used continuous glucose monitoring (CGM) in 15 patients newly diagnosed with GD to evaluate changes in glucose trends following improvement in the thyroid function. Methods At the time of the diagnosis of GD, each participant wore a CGM monitor for seven days, and the data recorded on days 3 to 5 were analyzed. The clinical status before treatment with antithyroid drugs was evaluated. Following successful treatment with antithyroid drugs and improvement of free thyroxine (fT4) to within the normal range, CGM was used again to evaluate the same variables after treatment. Results The primary outcome, the standard deviation (SD) of glucose, improved from a baseline value of 28.9±4.9 to a post-treatment value of 22.2±5.1 mg/dL (p=0.001). Other variables also improved after treatment, including the mean amplitude of glycemic excursion (MAGE), daily average glucose level, nocturnal average glucose level (0:00-05:59), maximum and minimum glucose, percent time with glucose at >140 mg/dL, and percent time with glucose at >180 mg/dL; however, the coefficient of variation (CV) and percent time with glucose at <70 mg/dL did not improve. A univariate analysis showed the significant correlation of the SD with TSH receptor antibody (TRAb) and 1,5-Anhydro-D-Glucitol (1,5-AG). Conclusions Our results showed that CGM-based markers of mean glucose and glucose variability improved with the improvement of the thyroid function in newly diagnosed GD patients treated with antithyroid drugs.

Circadian clock, diurnal glucose metabolic rhythm, and dawn phenomenon

The circadian clock provides cue-independent anticipatory signals for diurnal rhythms of baseline glucose levels and glucose tolerance. The central circadian clock is located in the hypothalamic suprachiasmatic nucleus (SCN), which comprises primarily GABAergic neurons. The SCN clock regulates physiological diurnal rhythms of endogenous glucose production (EGP) and hepatic insulin sensitivity through neurohumoral mechanisms. Disruption of the molecular circadian clock is associated with the extended dawn phenomenon (DP) in type 2 diabetes (T2D), referring to hyperglycemia in the early morning without nocturnal hypoglycemia. The DP affects nearly half of patients with diabetes, with poorly defined etiology and a lack of targeted therapy. Here we review neural and secreted factors in physiological diurnal rhythms of glucose metabolism and their pathological implications for the DP.

Association of sleep quality with glycemic variability assessed by flash glucose monitoring in patients with type 2 diabetes

BACKGROUND

Deterioration of sleep quality has been reported to contribute to the incidence of diabetes and may be responsible for glycemic status in diabetes. The present study explored the relationship between sleep quality and glycemic variability in patients with type 2 diabetes (T2D).

METHODS

We recruited 111 patients with T2D for this cross-sectional study. Each patient underwent flash glucose monitoring for 14 days to obtain glycemic variability parameters, such as standard deviation of glucose (SD), coefficient of variation of glucose (CV), mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD), and time in glucose range of 3.9-10 mmol/L (TIR_3.9-10). After 14 days of flash glucose monitoring, each patient received a questionnaire on the Pittsburgh Sleep Quality Index (PSQI) to evaluate subjective sleep quality. HbA1c was also collected to assess average glucose.

RESULTS

HbA1c was comparable among the subgroups of PSQI score tertiles. Across ascending tertiles of PSQI scores, SD, CV and MAGE were increased, while TIR_3.9-10 was decreased (p for trend  <  0.05), but not MODD (p for trend  =  0.090). Moreover, PSQI scores were positively correlated with SD, CV, MODD and MAGE (r =  0.322, 0.361, 0.308 and 0.354, respectively, p  <  0.001) and were inversely correlated with TIR_3.9-10 (r  =  - 0.386, p  <  0.001). After adjusting for other relevant data by multivariate linear regression analyses, PSQI scores were independently responsible for SD (β  =  0.251, t  =  2.112, p  =  0.041), CV (β  =  0.286, t  =  2.207, p  =  0.033), MAGE (β  =  0.323, t  =  2.489, p  =  0.018), and TIR_3.9-10 (β  =  - 0.401, t  =  - 3.930, p  <  0.001) but not for MODD (β  =  0.188, t  =  1.374, p  =  0.177).

CONCLUSIONS

Increased glycemic variability assessed by flash glucose monitoring was closely associated with poor subjective sleep quality evaluated by the PSQI in patients with T2D.

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.

High-normal serum thyrotropin levels and increased glycemic variability in type 2 diabetic patients

PURPOSE

High-normal thyrotropin (TSH) is related to reduced insulin sensitivity and may contribute to glycemic disorders in diabetes. We investigated the relationship between normal serum TSH levels and glycemic variability in euthyroid type 2 diabetic patients.

METHODS

A total of 432 newly diagnosed type 2 diabetic patients with euthyroid function and normal serum TSH levels were recruited between March 2013 and February 2017. Insulin sensitivity was evaluated by the Matsuda index (ISI_Matsuda) following a 75-g oral glucose tolerance test. Multiple glycemic variability indices, including the mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD), and standard deviation of glucose (SD), were calculated from glucose data obtained with a continuous glucose monitoring system. Average glucose accessed by 24-h mean glucose (24-h MG) was also calculated.

RESULTS

A normal serum TSH level was positively correlated with MAGE, MODD, SD, and 24-h MG (r = 0.206, 0.178, 0.186, and 0.132, respectively, p < 0.01). After adjusting for somatometric parameters, lipid profiles, ISI_Matsuda, and HbA1c via multiple linear regression analysis, mean differences [B(95% CI)] in MAGE, MODD, SD, and 24-h MG between the patients in the lowest and highest quartiles of TSH levels were 0.128(0.031, 0.226), 0.085(0.022, 0.148), 0.039(0.001, 0.078), and 0.002(-0.264, 0.267) mmol/L, respectively. High-normal TSH was independently associated with MAGE, MODD, and SD, but not 24-h MG.

CONCLUSIONS

High-normal serum TSH is a significant additional risk factor for increased glycemic variability in type 2 diabetic patients.

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.