The researchers of a 2020 study suggested that diabetic individuals must be routinely tested for thyroid dysfunctions.
Thyroid disorders and diabetes are relatively common health conditions that involve hormonal dysfunction and are treated by endocrinologists. The growing body of evidence indicates a positive association between the two conditions.
The endocrine system consists of eight major glands throughout the body, including the thyroid and the pancreas. The term “endocrine disorder” refers to a group of health conditions affecting hormonal production and release. In these disorders of the endocrine system, a hormone may be produced but does not function properly. People living with one of the conditions may be at an of developing the other. Both the conditions have several causes and can present with a wide spectrum of symptoms.
The thyroid gland is a butterfly-shaped gland situated on the front side of the neck and produces hormones such as triiodothyronine (T3) and thyroxine (T4), which regulate body metabolism, moods, and heart rate and breathing. In a few cases, the thyroid may overproduce hormones (hyperthyroidism), or underproduce hormones (hypothyroidism). Autoimmune conditions can often result in the development of thyroid disorders. Hashimoto’s thyroiditis and Graves’ disease are commonly reported causes of hypothyroidism and hyperthyroidism, respectively.
The pancreas is a gland situated in the abdomen which produces insulin, a hormone responsible for blood sugar levels, and enables peripheral utilization of sugar (glucose) in the blood by cells, supplying them with nutrition and energy to function. Diabetes refers to inadequate (type 2 ) or complete absence (type 1) of insulin production by the pancreas. Lifestyle factors, insulin resistance, and genetic constitution may contribute to diabetes development.
Commonly reported symptoms of diabetes include increased hunger, increased thirst, and frequent urination. Symptoms of hypothyroidism include dry skin, feeling tired and cold, and for hyperthyroidism, symptoms include sweating, thinning of the skin, and irritability.
Thyroid and Blood Sugar
The thyroid gland secretes hormones that regulate metabolism. An imbalance in thyroid hormones can affect an individual’s blood sugar. Among individuals with hyperthyroidism, blood sugar levels may spike rapidly after the consumption of meals.
Thyroxine stimulates glucagon release from the pancreas. Glucagon is a type of stored sugar, which the body when blood sugar levels are low (hypoglycemia). On the contrary, glucagon release is inhibited when blood sugar levels attain a healthy range. An overactive thyroid would release glucagon even when it is not required, and this release of stored sugar could increase an individual’s blood sugar levels. Glucagon excess is a key factor in diabetes development.
Thyroid and Insulin
Evidence suggests that there is an association between insulin resistance and hyperthyroidism and hypothyroidism. Since thyroid hormones are important for the metabolism of carbohydrates, thyroid dysfunction could impact insulin levels and lead to type 2 diabetes development.
Insulin resistance could occur subsequent to hyperthyroidism due to an increase in fatty free acids (FFA) in the blood. In body fat, thyroxine stimulates lipolysis, a process involving the breakdown of body fat into serum FFA. Research indicates a positive link between serum FFA levels and diabetes since the acids could pose a hindrance to the secretion of insulin and result in insulin resistance.
Research indicates that hypothyroidism could lead to insulin resistance partially since it limits the amount of insulin release (and glucose utilization by the muscles). Further, hypothyroidism can slow down metabolism, and therefore, insulin would stay in the blood longer.
Type 1 diabetes is closely associated with autoimmune-induced thyroid dysfunction (AITD). About 17–30% of adult individuals with type 1 diabetes also have AITD. In addition, 25% of children with type 1 diabetes have autoimmune hypothyroidism. Research indicates that genetic factors may contribute to this finding.
Another potential link between diabetes and thyroid disorders could be related to the hypothalamic-pituitary-adrenal (HPA) axis, or interactions of the hypothalamus, pituitary gland, and adrenal glands. These glands secrete hormones into the bloodstream and help in the management of stress responses by regulating cortisol hormone levels. Cortisol excess and HPA axis dysfunction could elevate blood sugar levels (hyperglycemia), cause insulin resistance, and reduce thyroid hormone levels.
Prevention and management
To prevent or delay the onset of type 2 diabetes, a nutritious and balanced diet, and regular physical exercise are essential. Diabetes self-care plans: medications and insulin injections as prescribed, attaining HbA1C targets, cholesterol and blood pressure management, and smoking cessation.
Individuals can manage thyroid dysfunction with medications. T4 replacement medications can increase T4 levels with TSH levels returning to a healthy level. Hyperthyroidism management therapies including antithyroid drugs, radioactive iodine, beta-blockers, and surgery could be opted for, based on the doctor’s advice.