Endocrinology · Metabolic Disorders
The facts most likely to be tested
Diagnostic criteria for Type 2 Diabetes Mellitus include a fasting plasma glucose ≥ 126 mg/dL, a 2-hour plasma glucose ≥ 200 mg/dL during an oral glucose tolerance test, or an HbA1c ≥ 6.5%.
Metformin is the first-line pharmacologic therapy for patients with Type 2 Diabetes due to its efficacy in lowering HbA1c and its favorable weight-neutral profile.
Patients with established atherosclerotic cardiovascular disease (ASCVD), heart failure, or chronic kidney disease should be prioritized for GLP-1 receptor agonists or SGLT2 inhibitors regardless of baseline HbA1c.
SGLT2 inhibitors are associated with a unique risk of euglycemic diabetic ketoacidosis and increased incidence of genitourinary tract infections.
GLP-1 receptor agonists provide significant cardiovascular risk reduction and promote weight loss but are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2.
Diabetic nephropathy is screened for via the urine albumin-to-creatinine ratio (UACR), and patients with albuminuria should be initiated on an ACE inhibitor or ARB for renal protection.
Diabetic retinopathy is the most common cause of new-onset blindness in adults and is characterized on fundoscopy by microaneurysms, dot-and-blot hemorrhages, and neovascularization.
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A 58-year-old male with a history of obesity presents for a routine physical. He reports increased thirst and frequent urination over the past three months. Physical exam reveals a BMI of 34 kg/m² and acanthosis nigricans on the posterior neck. Laboratory studies show a fasting plasma glucose of 142 mg/dL and an HbA1c of 7.2%. He has no history of cardiovascular disease or renal impairment.
What is the most appropriate initial pharmacologic therapy for this patient?
Metformin
The patient meets diagnostic criteria for Type 2 Diabetes Mellitus, and Metformin is the recommended first-line agent for patients without specific comorbidities like heart failure or CKD.
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High yield triage
Etiology / Epidemiology
Driven by insulin resistance and relative insulin deficiency. Primary risk factors: obesity, sedentary lifestyle, and family history.
Clinical Manifestations
Often asymptomatic; classic triad: polyuria, polydipsia, polyphagia. Acanthosis nigricans is a pathognomonic sign of insulin resistance.
Diagnosis
HbA1c ≥ 6.5% or Fasting Plasma Glucose ≥ 126 mg/dL on two separate occasions.
Treatment
Metformin is the first-line pharmacotherapy. Lactic acidosis is the rare but critical side effect.
Prognosis
Leading cause of end-stage renal disease and blindness. Target HbA1c < 7.0% for most adults.
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Epidemiology & Etiology
Prevalence is highest in patients with BMI > 30 and sedentary habits. Strong genetic component with high concordance in monozygotic twins. Pathogenesis involves progressive beta-cell failure superimposed on peripheral insulin resistance.
Pertinent Anatomy
The Islets of Langerhans in the pancreas are the primary site of dysfunction. Chronic hyperglycemia leads to microvascular damage in the retina, glomerulus, and peripheral nerves.
Pathophysiology
Peripheral tissues (muscle/adipose) develop resistance to insulin signaling. The liver increases gluconeogenesis despite elevated serum glucose. Eventually, pancreatic beta-cells exhaust, leading to a transition from hyperinsulinemia to relative insulin deficiency.
Clinical Manifestations
Patients often present with polyuria, polydipsia, and nocturia due to osmotic diuresis. Look for acanthosis nigricans in skin folds as a marker of hyperinsulinemia. Blurred vision and recurrent yeast infections are common initial complaints.
Diagnosis
The HbA1c ≥ 6.5% is the preferred diagnostic test. Alternatively, a Fasting Plasma Glucose ≥ 126 mg/dL or a 2-hour OGTT ≥ 200 mg/dL confirms the diagnosis. A random glucose ≥ 200 mg/dL with classic symptoms is also diagnostic.
Treatment
Initiate Metformin at diagnosis unless contraindicated by eGFR < 30 mL/min. Lactic acidosis risk mandates monitoring renal function. If glycemic targets are not met, add GLP-1 receptor agonists or SGLT2 inhibitors for cardiovascular and renal protection.
Prognosis
Chronic hyperglycemia causes microvascular (retinopathy, nephropathy, neuropathy) and macrovascular (CAD, stroke, PAD) disease. Annual dilated eye exams and microalbuminuria screening are mandatory for all patients.
Differential Diagnosis
Type 1 Diabetes: acute onset with weight loss and ketosis
MODY: autosomal dominant inheritance in young, non-obese patients
Cushing Syndrome: associated with central obesity and striae
Diabetes Insipidus: polyuria without hyperglycemia
Gestational Diabetes: onset during pregnancy