Diabetes due to endocrinopathies

Diabetes due to endocrinopathies is a specific type of diabetes in which hyperglycemia does not arise from the typical mechanism of type 1 diabetes mellitus or the classic mechanism of type 2 diabetes mellitus, but represents the metabolic consequence of an endocrine disorder characterized by hormone excess, less commonly by hormone deficiency, or by neuroendocrine abnormalities capable of substantially altering insulin secretion, insulin sensitivity, hepatic glucose production, and energy-substrate homeostasis. It is therefore a precise etiologic category in which the underlying endocrine disease acts as the pathophysiologic driver of the glycemic disorder. This framework mainly includes acromegaly, Cushing syndrome, pheochromocytoma, glucagonoma, somatostatinoma, hyperthyroidism, and, in certain settings, primary hyperaldosteronism and other endocrine conditions capable of increasing counterregulatory hormonal activity or impairing insulin secretion.

The clinical relevance of this category is greater than its relatively lower frequency compared with type 2 diabetes might suggest. Correct recognition of the etiologic relationship changes the entire diagnostic and therapeutic pathway because reducing blood glucose alone is insufficient in these patients: the core of management is identification and treatment of the responsible endocrine disorder. In many cases, diabetes improves or resolves after hormonal hypersecretion is controlled, whereas in others it persists because the endocrine disease has merely accelerated the emergence of pre-existing metabolic vulnerability. Diabetes due to endocrinopathies should therefore be interpreted as a form of secondary diabetes in which endocrine and diabetologic diagnosis necessarily proceed together.

The epidemiology of diabetes due to endocrinopathies is difficult to summarize in a single estimate because it depends on the underlying disease, duration of exposure to hormone excess, patient age, degree of pre-existing metabolic predisposition, and the criteria used to define dysglycemia, impaired glucose tolerance, and overt diabetes. Recent literature and the 2025 Italian endocrine position statement emphasize that glycemic disorders are particularly common in endocrinopathies involving excess counterregulatory hormones, especially acromegaly and Cushing syndrome, but may also occur in pheochromocytoma, hyperthyroidism, and neuroendocrine tumors that secrete glucagon or somatostatin.

In acromegaly, the prevalence of impaired glucose tolerance and diabetes mellitus is high because excess growth hormone and insulin-like growth factor 1 (IGF-1) profoundly disrupt the balance between insulin sensitivity and beta-cell compensatory capacity. Similarly, in Cushing syndrome, chronic hypercortisolism promotes extensive metabolic remodeling, with increased gluconeogenesis, visceral adiposity, loss of muscle mass, and widespread insulin resistance. In both disorders, diabetes is not an incidental comorbidity, but one of the principal systemic manifestations of hormone excess.

In pheochromocytoma and paraganglioma, hyperglycemia may result from chronic or paroxysmal catecholamine excess, which reduces insulin secretion, increases hepatic glucose production, and enhances lipolysis. In glucagonoma, the mechanism is even more direct because excess glucagon strongly promotes hepatic gluconeogenesis and glycogenolysis. In somatostatinoma, by contrast, the glycemic defect primarily results from inhibition of insulin and other gastrointestinal hormone secretion. Hyperthyroidism more often unmasks or worsens pre-existing dysglycemia than causes severe isolated diabetes, but in predisposed patients it may be the factor that pushes the system beyond the clinical threshold.

These forms are clinically important because they are often initially misclassified as type 2 diabetes, especially when the endocrine disorder has not yet been diagnosed. The risk is twofold: identification of the responsible endocrinopathy is delayed, and diabetes treatment may not fully correspond to the dominant pathophysiologic mechanism. Correct evaluation reduces this risk and allows hyperglycemia to be understood as a systemic endocrine signal rather than a merely isolated metabolic disorder.

The pathophysiology of diabetes due to endocrinopathies centers on a common principle: hormone excess disrupts the normal balance among insulin secretion, peripheral insulin sensitivity, hepatic glucose output, and regulation of lipid and protein metabolism. The actual mechanisms, however, differ substantially from one disorder to another, making detailed etiopathogenetic reasoning necessary. Insulin resistance predominates in some endocrinopathies, reduced insulin secretion in others, and both processes coexist in still others.

In acromegaly, excess growth hormone acts as a potent counterregulatory factor. Skeletal muscle reduces glucose utilization, the liver increases endogenous glucose production, adipose tissue increases lipolysis, and the resulting flux of free fatty acids further impairs insulin signaling. Initially, beta cells may compensate by increasing insulin secretion, but this adaptation eventually becomes insufficient, particularly in individuals with genetic predisposition, obesity, or older age. IGF-1 has more complex metabolic effects, some of which are insulin-like, but in the overall clinical setting of acromegaly it cannot neutralize the marked insulin resistance caused by growth-hormone excess.

In Cushing syndrome, excess cortisol enhances hepatic gluconeogenesis, reduces peripheral glucose uptake, promotes proteolysis and lipolysis, increases the supply of gluconeogenic substrates, and drives central fat redistribution. The result is a strongly diabetogenic environment in which the pancreas must sustain a high and persistent demand for insulin. When compensatory capacity is no longer sufficient, impaired glucose tolerance and overt diabetes develop. Chronic hypercortisolism is also associated with sarcopenia, visceral adiposity, low-grade inflammation, and deterioration of other cardiometabolic factors, making the clinical picture even more complex.

In pheochromocytoma, catecholamines reduce insulin secretion primarily through alpha-adrenergic activation, increase hepatic glycogenolysis and gluconeogenesis, stimulate lipolysis, and increase peripheral insulin resistance. Even when hyperglycemia is not constant, wide glycemic fluctuations may occur, particularly in patients with intermittent catecholamine surges. In primary hyperaldosteronism, the diabetogenic contribution is more indirect but clinically relevant: aldosterone excess is associated with insulin resistance, inflammation, oxidative stress, and, in cases with hypokalemia, possible reduction of insulin secretion.

In glucagonoma, the pathophysiology is almost paradigmatic: excess glucagon amplifies hepatic glucose output and promotes a persistent catabolic state. In somatostatinoma, excess somatostatin inhibits secretion of insulin, glucagon, gastrin, cholecystokinin, and other entero-pancreatic hormones, producing a complex syndrome in which diabetes is associated with maldigestion, steatorrhea, and nutritional abnormalities. In hyperthyroidism, elevated thyroid hormones accelerate intestinal glucose absorption, hepatic output, insulin turnover, and lipolysis, facilitating the emergence of dysglycemia particularly in already predisposed individuals. The common thread is always the same: the endocrine disease systemically alters glucose physiology, and diabetes becomes a clinically recognizable consequence.

Clinical manifestations should be read in chronological order, as they would be during an actual consultation. In the medical history, the patient may report nonspecific symptoms of hyperglycemia such as polyuria, polydipsia, weight loss, fatigue, blurred vision, or increased susceptibility to infection. In diabetes due to endocrinopathies, however, these symptoms are rarely isolated. More often they occur within a clinical context dominated by signs and symptoms of the responsible endocrine disease, and this combination is the principal diagnostic clue.

In a patient with acromegaly, for example, the clinical history may reveal progressive enlargement of the hands and feet, changes in facial features, headache, snoring, carpal tunnel syndrome, sweating, and arthralgia, accompanied over time by glycemic abnormalities. In Cushing syndrome, the history may instead include centripetal weight gain, easy bruising, proximal muscle weakness, hypertension, mood disturbances, and skin fragility, with hyperglycemia often accompanied by dyslipidemia and worsening blood pressure. In pheochromocytoma, hyperglycemia may occur alongside episodes of headache, palpitations, sweating, and paroxysmal or sustained hypertension.

During the physical examination, the clinician should therefore look not only for general signs of diabetes, but above all for the phenotypic signs of the endocrinopathy. The appearance of the face and extremities, body-fat distribution, the presence of violaceous striae, hypertension, tremor, tachycardia, skin pigmentation, loss of muscle mass, skin nodules, or signs of malnutrition become an integral part of the diabetes assessment. In other words, the patient’s body often suggests the endocrine diagnosis before second-line tests are performed.

The severity of hyperglycemia varies. Many patients have moderate dysglycemia or diabetes that superficially resembles type 2 disease. Others, particularly those with glucagon-secreting neuroendocrine tumors or severe hypercortisolism, may develop marked weight loss, catabolism, dehydration, and more severe metabolic decompensation. Diabetic ketoacidosis is not the most typical initial presentation, but it cannot be excluded when insulin deficiency or the counterregulatory hormonal burden becomes extreme. The essential point is that the clinical features of diabetes should never be separated from those of the endocrine disorder because the two components explain one another.

Diabetes due to an endocrinopathy should be suspected when hyperglycemia is associated with a clinical picture that cannot be fully explained by ordinary type 2 diabetes. The first clue is the presence of specific endocrine signs or symptoms, such as an acromegalic phenotype, cushingoid stigmata, adrenergic crises, thyrotoxicosis, diarrhea with weight loss, necrolytic migratory erythema, or persistent hypokalemia. The second is the development of diabetes in relatively lean patients or in individuals with clinical features unusual for common type 2 diabetes. The third is difficulty explaining the glycemic disorder solely through traditional metabolic risk factors.

The medical history should be highly detailed and not limited to classic diabetes risk factors. Questions should address progressive somatic changes, altered facial appearance, increases in shoe or ring size, hypertensive crises, episodes of sweating and palpitations, weight loss despite hyperphagia, proximal muscle weakness, changes in bowel habits, unusual skin rashes, menstrual irregularities, erectile dysfunction, fragility fractures, or a family history of endocrine neoplasms. The course of diabetes is also informative: rapid onset coinciding with a systemic endocrine syndrome should always suggest a secondary form.

Features that strongly suggest diabetes secondary to an endocrinopathy

• Diabetes or dysglycemia associated with phenotypic signs of acromegaly, Cushing syndrome, thyrotoxicosis, or pheochromocytoma
• Hyperglycemia in the presence of a known or suspected neuroendocrine tumor
• Poor concordance between the severity of the glycemic disorder and the patient’s usual metabolic profile
• Improvement in glycemic control after treatment of the underlying endocrinopathy

Suspicion should be even stronger when diabetes develops together with difficult-to-control hypertension, hypokalemia, loss of muscle mass, catabolic weight loss, or systemic endocrine symptoms. In such cases, the issue is not merely to establish whether the patient has diabetes, but to determine whether diabetes is the expression of a potentially treatable or even curable endocrine disease. This step is decisive because it shifts attention from lowering blood glucose to identifying the causal process.

Diagnosis is constructed in two stages. The first is documentation of the glycemic disorder according to the general criteria for diabetes mellitus. The 2026 ADA Standards of Care confirm that diabetes can be diagnosed using fasting plasma glucose, the 2-hour plasma glucose value after an oral glucose tolerance test (OGTT), glycated hemoglobin (HbA1c), or a random plasma glucose value in the presence of classic symptoms of hyperglycemia or a hyperglycemic crisis. The second stage, which is the more important in this category, is to demonstrate that diabetes is secondary to a specific endocrinopathy rather than merely concomitant.

First-line investigations therefore include standard diabetes tests together with clinical and biochemical assessment guided by the endocrine hypothesis. If the patient has acromegalic features, evaluation includes IGF-1 measurement and appropriate dynamic tests. If the presentation suggests hypercortisolism, recommended tests for Cushing syndrome are performed, such as a dexamethasone suppression test, late-night salivary cortisol, or urinary free cortisol, according to the context. If pheochromocytoma is suspected, the rational next step is measurement of plasma free or fractionated urinary metanephrines. In thyrotoxicosis, thyroid-stimulating hormone (TSH) and free thyroid hormones are assessed. In suspected neuroendocrine tumors, investigations are tailored to the secretory profile and appropriate imaging.

There are no single, separate official diagnostic criteria for “diabetes due to endocrinopathies” as an overall category because the etiologic diagnosis depends on the individual causal disease. In the absence of criteria specific to the umbrella category, the correct approach is an integrated clinical and etiologic diagnosis: according to available reviews and documents, diagnosis of diabetes secondary to an endocrinopathy requires demonstration of diabetes or dysglycemia using standard diabetes criteria together with documentation of an endocrine disease plausibly capable of causing it, a coherent pathophysiologic relationship, and, when possible, metabolic improvement after treatment of the underlying disorder.

The differential diagnosis includes concomitant type 2 diabetes mellitus, diabetes induced by medications used to treat the endocrine disorder, stress hyperglycemia, pancreatic disease, and other specific types of diabetes. In some patients the boundary is not sharp because the endocrinopathy does not cause diabetes by itself but accelerates an already vulnerable metabolic substrate. Even in such cases, the diagnosis remains clinically useful because it assigns the appropriate causal weight to hormone excess and directs therapy toward the etiologic target.

In practical terms, diabetes due to endocrinopathies can be classified according to the dominant endocrine mechanism. A first major category includes forms caused by excess counterregulatory hormones, such as acromegaly, Cushing syndrome, pheochromocytoma, and glucagonoma. Increased hepatic glucose output, lipolysis, proteolysis, and insulin resistance predominate in these conditions. A second category includes forms dominated by inhibition of insulin secretion, as occurs in somatostatinoma and, in part, in pheochromocytoma or hyperaldosteronism with significant hypokalemia. A third category includes forms in which the endocrinopathy unmasks or amplifies pre-existing metabolic vulnerability, as often occurs in hyperthyroidism.

A further classification distinguishes potentially reversible from only partially reversible forms. In pheochromocytoma, for example, removal of the tumor may produce marked improvement or even remission of diabetes in some patients. Control of the endocrine disease also often substantially reduces dysglycemia in acromegaly and Cushing syndrome. Reversibility should never be assumed, however, because duration of hormonal exposure, age, obesity, genetics, and beta-cell reserve affect the possibility of recovery. In other words, endocrine control improves pathophysiology but does not always erase established metabolic injury.

Nosologically, these conditions fall within the other specific types of diabetes in modern diabetes classification, but that label is only a starting point. In practice, the clinician must always identify the individual endocrinopathy because epidemiology, mechanism, prognosis, and treatment differ profoundly among diseases. The generic term “diabetes due to an endocrinopathy” is useful for guiding reasoning, but is never sufficient to determine clinical management.

Treatment must always pursue two parallel objectives: control hyperglycemia and treat the causal endocrinopathy. This rule is more important here than in almost any other form of secondary diabetes. If clinicians prescribe glucose-lowering medications without addressing hormone excess, glucose metabolism will continue to be driven toward dysfunction by the principal pathogenetic mechanism. Recent reviews emphasize precisely this point: in diabetes due to endocrinopathies, correction of hormonal imbalance is not an ancillary component, but the cornerstone of the metabolic strategy.

In the short term, selection of glucose-lowering therapy depends on the predominant mechanism, severity of hyperglycemia, and clinical stability. When insulin resistance predominates, as in acromegaly or Cushing syndrome, metformin is often a rational foundation if not contraindicated because it reduces hepatic glucose production and improves insulin sensitivity. Insulin may be required in more severe or unstable cases, particularly when the patient is catabolic, symptomatic, or awaiting definitive treatment of the endocrine disease. Glucagon-like peptide 1 receptor agonists or other medications may be useful in selected patients, but treatment must always be individualized according to the endocrine context and comorbidities.

Etiologic therapy naturally differs among disorders. Acromegaly may be treated with pituitary surgery, somatostatin analogues, GH-receptor antagonists, or other specific strategies; in Cushing syndrome, treatment aims to remove the source of hypercortisolism or control it pharmacologically; in pheochromocytoma, surgery after adequate adrenergic blockade is decisive; in glucagon- or somatostatin-secreting neuroendocrine tumors, oncologic and surgical treatment directly modifies the glycemic profile; and in hyperthyroidism, control of thyrotoxicosis reduces the counterregulatory burden. In all these settings, improvement in diabetes is often one indicator of successful endocrine treatment.

An important consideration is that some endocrine treatments may themselves modify glucose metabolism favorably or unfavorably. Certain somatostatin analogues, for example, can affect insulin secretion; medications used for hypercortisolism may alter body weight and glucose-treatment requirements; and curative surgery may improve diabetes rapidly, making reduction of glucose-lowering therapy necessary. This requires close monitoring and dynamic management. Metabolic therapy in diabetes due to endocrinopathies is almost never static: care must adapt to the evolution of the underlying disease and its treatments.

Follow-up should be integrated between diabetology and endocrinology. The first objective is to monitor the glycemic response to treatment of the endocrinopathy. In many patients, reduction of hormone excess improves the glycemic profile within weeks or months, but the extent of recovery varies greatly. Glucose values, HbA1c, body weight, and glucose-lowering therapy should therefore be reassessed regularly, with particular attention to hypoglycemia in patients who improve rapidly after surgery or effective medical treatment.

The second objective is to assess the course of the underlying endocrine disease. Recurrence of acromegaly, persistent hypercortisolism, incomplete treatment of pheochromocytoma, or progression of a neuroendocrine tumor may also manifest as renewed metabolic deterioration. Diabetes thus becomes a genuine clinical biomarker of the quality of endocrine control. A rise in blood glucose in a previously stable patient should therefore not be interpreted only as failure of diabetes management, but also as a possible sign of persistent or recurrent endocrine disease.

Follow-up should also include surveillance of cardiovascular risk factors because many diabetogenic endocrinopathies share a substantial vascular burden with diabetes. Hypertension, dyslipidemia, visceral adiposity, hepatic steatosis, sarcopenia, and systemic inflammation may persist even after glycemic control improves. Follow-up visits should therefore be systemic rather than confined to blood glucose. This is particularly important in acromegaly and Cushing syndrome, where cardiometabolic injury is often multidimensional.

Over the medium and long term, it is necessary to establish whether the patient has achieved remission of diabetes, merely reduced treatment requirements, or persistent diabetes despite endocrine control. This distinction has prognostic and practical value. Persistent hyperglycemia does not necessarily indicate failure of endocrine treatment, but may show that the endocrinopathy has unmasked an underlying diabetes that has become autonomous. Follow-up should therefore be sufficiently prolonged and should not stop as soon as the endocrine disease appears controlled.

The prognosis of diabetes due to endocrinopathies depends on the combination of three main factors: the type of endocrinopathy, how rapidly the underlying disease is controlled, and the patient’s degree of pre-existing metabolic vulnerability. In general, the earlier hormone excess is corrected, the greater the likelihood that diabetes will improve. Conversely, prolonged exposure to counterregulatory hormones or catabolic neuroendocrine states increases the probability that metabolic injury will become persistent.

Immediate complications do not depend only on elevated blood glucose, but also on the fact that it occurs in an organism already altered by the endocrinopathy. In acromegaly and Cushing syndrome, diabetes adds to hypertension, dyslipidemia, structural heart disease, obstructive sleep apnea, and increased thrombotic or cardiovascular risk. In pheochromocytoma, it occurs in a setting of hemodynamic instability and adrenergic risk. In neuroendocrine tumors, it may be associated with cachexia, malnutrition, or complex secretory syndromes. The overall clinical burden is therefore often greater than the simple sum of the individual diagnoses.

Over the long term, if hyperglycemia persists, the patient enters the same continuum of microvascular and macrovascular risk as in other forms of diabetes, with potential renal, retinal, neurologic, and cardiovascular involvement. In diabetogenic endocrinopathies, however, this risk must be interpreted more broadly because it coexists with organ damage caused by the endocrine disease itself. Prognosis therefore depends not only on HbA1c, but on combined control of metabolism and the endocrinopathy.

In summary, diabetes due to endocrinopathies is a form of secondary diabetes in which optimal glycemic control inevitably depends on controlling the hormonal cause. Prognosis is better the earlier the clinician recognizes the condition, avoids reductively labeling it as ordinary type 2 diabetes, and constructs a genuinely integrated diagnostic and therapeutic pathway. The decisive point is not merely to treat blood glucose, but to stop the endocrine driver that generates it.