Diabetes, Hashimoto’s, and an underactive thyroid
The autoimmune connection between an underactive thyroid, excessive weight, and diabetes
Thyroid conditions and diabetes are the two most frequent hormonal problems general practitioners encounter in their daily practice (1).
Today diabetes is grouped in two main forms: type 1 and type 2 diabetes. Both type 1 and 2 diabetes can occur in people diagnosed with Hashimoto’s and an underactive thyroid (1).
Thyroid function and diabetes
Thyroid hormones are necessary for the body to metabolize carbohydrates, as well as for the pancreas to properly function (the organ producing insulin). Low thyroid hormones cause a drop in insulin levels — insulin is a hormone needed to take sugar from the blood to different cells throughout the body.
Low insulin levels cause high blood sugar levels and slows down in cellular function, including muscle contractions and basic brain function. Over longer periods of time low insulin levels can trigger diabetes.
People are at an increased risk of frequent hypoglycemic episodes with an underactive thyroid and low blood sugar symptoms include:
A feeling of hunger
Loss of consciousness (in extreme cases) (2–4).
Both clinical and subclinical hypothyroidism are connected to insulin resistance, a state where cells in the body stop responding to insulin’s signal to take sugar out of the blood. This results in high blood sugar levels, directly increasing the risk of eye damage and kidney damage (2–4). Insulin resistance can cause the thyroid gland to develop more nodules and become larger in size (5, 6).
Symptoms of insulin resistance include:
Weight gain (especially around the belly)
High blood pressure
People who are diagnosed with diabetes, but are not managing it through lifestyle interventions, are at risk of having lower levels of T3 hormone and high rT3 levels (7,8).
Hashimoto’s and type 1 diabetes
Type 1 diabetes is the most common chronic hormonal condition in children and young people — 4 in 100 children with diabetes type 1 also have Hashimoto’s (9). 1 in 2 relatives of people with type 1 diabetes have an autoimmune thyroid condition (10 -12).
4 in 10 adult patients with type 1 diabetes test positive for TPO antibodies, and are at risk for developing an underactive thyroid (13–15). Type 1 diabetes patients who test positive for glutamic acid decarboxylase antibodies (GADA) have a three and half times higher risk of developing a thyroid condition (16).
3 in 10 adults diagnosed with Hashimoto’s have type 1 diabetes — only half of these patients will have an underactive thyroid, while the other half will have TSH within normal ranges (10, 17).
Type 1 diabetes and Hashimoto’s co-occur often and are inherited, as they share several genes, whose mutation increases the risk of developing either type 1 diabetes, Hashimoto’s, or both (18–25).
Type 1 diabetes patients at an increased risk of developing Hashimoto’s and an underactive thyroid include (17, 26–31):
Positive for glutamic acid decarboxylase antibodies (GADA)
Have had type 1 diabetes for a long time
Hashimoto’s and type 2 diabetes
1 in 10 people with diabetes type 2 will have a thyroid condition too. Women with type 2 diabetes are five times more likely to have Hashimoto’s (32).
The American Thyroid Association guidelines for type 2 diabetes patients advises for frequent thyroid function testing (17).
Risk factors of having both type 2 diabetes and Hashimoto’s include:
High TPO antibodies in thyroid patients
High estrogen levels and polycystic ovary syndrome (PCOS)
Overweight and obesity
Metformin — a medication used to treat patients with type 2 diabetes, obesity, and/or people with PCOS — can normalize TSH levels in diabetic patients with an underactive thyroid (33).
Diabetes is a broad condition with many genetic and environmental triggers, as well as many symptoms and co-occurring conditions. A year ago researchers have further classified diabetes in five instead of two groups, and some of them are more associated with autoimmune conditions (34).
Tracking symptoms, including weight, energy, and focus in the BOOST Thyroid app may help you with your next doctor’s appointment.
Hage M, et al. Thyroid disorders and diabetes mellitus, 2011
Dimitriadis G, et al. Insulin action in adipose tissue and muscle in hypothyroidism, 2006
Cettour-Rose P, et al. Hypothyroidism in rats decreases peripheral glucose utilisation, a defect partially corrected by central leptin infusion, 2005
Maratou E, et al. Studies of insulin resistance in patients with clinical and subclinical hypothyroidism, 2009
Rezzonico J, et al. Introducing the thyroid gland as another victim of the insulin resistance syndrome, 2008
Ayturk S, et al. Metabolic syndrome and its components are associated with increased thyroid volume and nodule prevalence in a mild-to-moderate iodine-deficient area, 2009
Coiro V, et al. Influence of residual C-peptide secretion on nocturnal serum TSH peak in well-controlled diabetic patients, 1997
Donckier JE. Endocrine diseases and diabetes, 2003
Radetti G, et al. Frequency of Hashimoto’s thyroiditis in children with type 1 diabetes mellitus, 1995
McCanlies E, et al. Hashimoto’s thyroiditis and insulin-dependent diabetes mellitus: differences among individuals with and without abnormal thyroid function, 1998
Burek CL, et al. Thyroid autoantibodies in black and in white children and adolescents with type 1 diabetes mellitus and their first degree relatives, 1990
Sougioultzoglou F, et al. Coincidence of high antiislet and antithyroid autoantibody titles in first-degree relatives of patients with type 1 diabetes, 2005
Kordonouri O, et al. Predictivity of thyroid autoantibodies for the development of thyroid disorders in children and adolescents with Type 1 diabetes, 2002
Kordonouri O, et al. Natural course of autoimmune thyroiditis in type 1 diabetes: association with gender, age, diabetes duration, and puberty, 2005
Lindberg B, et al. High prevalence of thyroid autoantibodies at diagnosis of insulin-dependent diabetes mellitus in Swedish children, 1997
Kordonouri O, et al. GADA positivity at onset of type 1 diabetes is a risk factor for the development of autoimmune thyroiditis, 2011
Perros P, et al. Frequency of thyroid dysfunction in diabetic patients: value of annual screening, 1995
Holl RW, et al. Thyroid autoimmunity in children and adolescents with type 1 diabetes mellitus, 1999
Santamaria P, et al. HLA-DQB1-associated susceptibility that distinguishes Hashimoto’s thyroiditis from Graves’ disease in type I diabetic patients, 1994
Kim EY, et al. Polymorphisms of HLA class II predispose children and adolescents with type 1 diabetes mellitus to autoimmune thyroid disease, 2003
Levin L, et al. Analysis of HLA genes in families with autoimmune diabetes and thyroiditis, 2004
Dittmar M, et al. Early onset of polyglandular failure is associated with HLA-DRB1∗03, 2008
Golden B, et al. Genetic analysis of families with autoimmune diabetes and thyroiditis: evidence for common and unique genes, 2005
Ikegami H, et al. The association of CTLA4 polymorphism with type 1 diabetes is concentrated in patients complicated with autoimmune thyroid disease: a multicenter collaborative study in Japan, 2006
Dultz G, et al. The protein tyrosine phosphatase non-receptor type 22 C1858T polymorphism is a joint susceptibility locus for immunthyroiditis and autoimmune diabetes, 2009
Jung ES, et al. Thyroid autoimmunity in children and adolescents with newly diagnosed type 1 diabetes mellitus, 2014
Reghina AD, et al. Thyroid autoimmunity in 72 children with type 1 diabetes mellitus: relationship with pancreatic autoimmunity and child growth, 2012
Lee SM, et al. Clinical characteristics of autoimmune thyroid disease developed in patients with type 1 diabetes mellitus, 2005
Libman IM, et al. Thyroid autoimmunity in children with features of both type 1 and type 2 diabetes, 2008
Mantovani RM, et al. Thyroid autoimmunity in children and adolescents with type 1 diabetes mellitus: prevalence and risk factors, 2007
Kordonouri O, et al. Thyroid autoimmunity in children and adolescents with type 1 diabetes: a multicenter survey, 2002
Fleiner HF, et al. Prevalence of Thyroid Dysfunction in Autoimmune and Type 2 Diabetes: The Population-Based HUNT Study in Norway, 2016.
Cappelli C, et al. TSH-lowering effect of metformin in type 2 diabetic patients: differences between euthyroid, untreated hypothyroid, and euthyroid on L-T4 therapy patients, 2009
Ahlquist E, et al. Novel subgroups of adult-onset diabetes and their association with outcomes: a data-driven cluster analysis of six variables, 2018