Which condition is characterized by abnormally elevated blood sugar levels?

Diabetes mellitus is characterized by abnormally elevated blood sugar levels, a condition known as hyperglycemia. This can occur due to either insufficient insulin production by the pancreas or the body's cells becoming resistant to insulin's effects. In diabetes, the regulation of glucose metabolism is disrupted, leading to increased glucose concentrations in the bloodstream.

There are several types of diabetes, including type 1, where the body produces little or no insulin, and type 2, which is often characterized by insulin resistance. Regardless of the type, the commonality across all forms of diabetes is the inability to properly manage blood sugar levels, which over time can lead to various complications affecting the eyes, kidneys, nerves, and other systems in the body.

The other conditions listed do not directly cause elevated blood sugar levels. Hypothyroidism primarily affects metabolism and can lead to various symptoms, but it does not directly cause hyperglycemia. Adrenal insufficiency, while causing symptoms such as fatigue and weakness, is more associated with low cortisol levels impacting various bodily functions rather than direct changes in blood sugar levels. Thyroiditis refers specifically to inflammation of the thyroid gland and is likewise not directly related to elevated blood sugar.