A 62-year-old man presents to the emergency department with confusion. The patient’s wife states that her husband has become more somnolent over the past several days and now is very confused. The patient has no complaints himself, but is answering questions inappropriately. The patient has a past medical history of diabetes and hypertension. His temperature is 98.3°F (36.8°C), blood pressure is 127/85 mmHg, pulse is 138/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam is notable for a confused man with dry mucous membranes. Initial laboratory studies are ordered as seen below. Serum: Na+: 135 mEq/L Cl-: 100 mEq/L K+: 3.0 mEq/L HCO3-: 23 mEq/L BUN: 30 mg/dL Glucose: 1,299 mg/dL Creatinine: 1.5 mg/dL Ca2+: 10.2 mg/dL Which of the following is the most appropriate initial treatment for this patient?

Insulin, normal saline, and potassium

A 16-year-old woman presents to the emergency department for evaluation of acute vomiting and abdominal pain. Onset was roughly 3 hours ago while she was sleeping. She has no known past medical history. Her family history is positive for hypothyroidism and diabetes mellitus in her maternal grandmother. On examination, she is found to have fruity breath and poor skin turgor. She appears fatigued and her consciousness is slightly altered. Laboratory results show a blood glucose level of 691 mg/dL, sodium of 125 mg/dL, and elevated serum ketones. Of the following, which is the next best step in patient management?

Administer IV fluids and insulin

Initiate basal-bolus insulin regimen

Initiate insulin glargine 10 units at bedtime only

Initiate oral antidiabetic medications

Initiate insulin aspart at mealtimes only

A 56-year-old man presents for a follow-up regarding his management for type 2 diabetes mellitus (DM). He was diagnosed with type 2 DM about 7 years ago and was recently started on insulin therapy because oral agents were insufficient to control his glucose levels. He is currently following a regimen combining insulin lispro and neutral protamine Hagedorn (NPH) insulin. He is taking insulin lispro 3 times a day before meals and NPH insulin once in the morning. He has been on this regimen for about 2 months. He says that his glucose reading at night averages around 200 mg/dL and remains close to 180 mg/dL before his shot of NPH in the morning. The readings during the rest of the day range between 100–120 mg/dL. The patient denies any changes in vision or tingling or numbness in his hands or feet. His latest HbA1C level was 6.2%. Which of the following adjustments to his insulin regimen would be most effective in helping this patient achieve better glycemic control?

Add another dose of NPH in the evening.

Add another dose of insulin lispro in the evening.

Reduce a dose of insulin lispro.

Replace lispro with insulin aspart.

Add insulin glargine to the current regimen.

A 28-year-old man is brought in by ambulance to the ER, barely conscious, after feeling drowsy and falling to the floor during a presentation several hours ago. His colleague who accompanied him says he has had similar episodes 5 times in the past 3 months. No significant past medical history. His blood pressure is 110/80 mm Hg and pulse is 114/min. His capillary blood glucose is 15 mg/dL. Immediate IV dextrose with thiamine is started, and he rapidly regains consciousness. A contrast CT of the abdomen is performed which reveals a tumor in the pancreas. Which of the following relative laboratory findings would you most likely expect to find in this patient?

Glucose: ↓, Insulin: ↑, C-Peptide: ↑, Ketoacidosis: Absent

Glucose: ↑, Insulin: ↓, C-Peptide: ↓, Ketoacidosis: Present

Glucose: Normal, Insulin: Normal, C-Peptide: Normal, Ketoacidosis: Absent

Glucose: ↓, Insulin: ↑, C-Peptide: ↓, Ketoacidosis: Absent

Glucose: ↑, Insulin: ↑/Normal, C-Peptide: ↑/Normal, Ketoacidosis: Absent

A 71-year-old male is admitted to the hospital with a Staphylococcal aureus infection of his decubitus ulcers. He is diabetic and has a body mass index of 45. His temperature is 37°C (98.6°F), respirations are 15/min, pulse is 67/min and blood pressure is 122/98 mm Hg. The nurse is monitoring his blood glucose and records it as 63 mg/dL. She then asks the resident on call if the patient should receive glargine insulin as ordered seeing his glucose levels. Which of the following would be the most appropriate response by the resident?

No, glargine insulin should not be given during an episode of hypoglycemia as it will further lower blood glucose.

No, due to his S. aureus infection he is more likely to have low blood glucose and glargine insulin should be held until he has recovered.

No, glargine insulin was probably ordered in error as it is not recommended in type 2 diabetes.

No, glargine insulin should be stopped and replaced with lispro insulin until his blood glucose increases.

Yes, glargine insulin is a long-acting insulin and should still be given to control his blood glucose over the next 24 hours.

A researcher is tracing the fate of C-peptide, a product of preproinsulin cleavage. Which of the following is a true statement regarding the fate of C-peptide?

C-peptide is packaged with insulin in secretory vesicles

C-peptide exits the cells via a protein channel

C-peptide is further cleaved into insulin

C-peptide is immediately degraded by the proteasome

C-peptide activates an intracellular signaling cascade

Insulin preparations and kinetics for USMLE Step 3: High-Yield Pharmacology Lessons

Insulin Synthesis - The Body's Sugar Boss

Insulin synthesis and secretion in pancreatic beta cell

Origin: Synthesized in pancreatic β-cells, encoded by the INS gene on chromosome 11.
Process: Follows the secretory pathway from preproinsulin (RER) to proinsulin (Golgi), finally cleaved into active insulin and C-peptide.
Storage: Held in secretory granules with zinc, awaiting a glucose signal for release.

⭐ C-peptide is the most accurate measure of endogenous insulin production. It has a longer half-life (~~30 min) than insulin (~~5 min), making it a more stable clinical marker.

Insulin Kinetics - The Insulin Lineup

Insulin kinetics: onset, peak, and duration by type

Rapid-Acting: Lispro, Aspart, Glulisine. 📌 Mnemonic: No LAG.
- Onset: 15 min
- Peak: 1-2 hr
- Duration: 3-5 hr
Short-Acting: Regular (Humulin R, Novolin R).
- Onset: 30-60 min
- Peak: 2-4 hr
- Duration: 6-8 hr
Intermediate-Acting: NPH (Humulin N, Novolin N).
- Onset: 1-2 hr
- Peak: 4-12 hr
- Duration: 12-18 hr
Long-Acting: Detemir, Glargine, Degludec.
- Onset: 1-2 hr
- Peak: Flat (no true peak)
- Duration: >24 hr (Glargine, Degludec), 16-24 hr (Detemir)

⭐ IV regular insulin is standard for hyperglycemic emergencies like DKA, while rapid-acting (Lispro/Aspart) can also be used IV.

Clinical Use & Complications - The Balancing Act

Therapeutic Uses:
- Type 1 & advanced Type 2 DM
- Gestational Diabetes
- DKA/HHS emergencies
- Hyperkalemia (with glucose to prevent hypoglycemia)
Major Complications:
- Hypoglycemia: Most common/dangerous.
  - Autonomic symptoms (tachycardia, sweating) precede neuroglycopenic ones (confusion, coma).
  - Treat: Glucose (oral/IV), glucagon (IM).
- Weight Gain: Due to anabolic effects.
- Lipodystrophy: Atrophy/hypertrophy at injection sites; prevented by site rotation.
- Hypokalemia: Especially with IV insulin; drives K⁺ into cells.

⭐ Exam Favorite: Differentiating morning hyperglycemia. Check glucose at 3 AM.

Somogyi Effect: Low 3 AM glucose. Caused by nocturnal hypoglycemia → counter-regulatory surge. Fix: Decrease evening insulin.

Dawn Phenomenon: Normal/High 3 AM glucose. Caused by morning cortisol/GH surge. Fix: Increase evening insulin.

Somogyi Effect vs. Dawn Phenomenon vs. Underbasalization

High‑Yield Points - ⚡ Biggest Takeaways

Rapid-acting insulins (Lispro, Aspart, Glulisine) are crucial for postprandial glucose control.

Regular insulin is the only preparation for IV use, making it essential in Diabetic Ketoacidosis (DKA).

NPH, an intermediate-acting insulin, has a cloudy appearance and exhibits more variable absorption.

Long-acting, peakless insulins (Glargine, Detemir, Degludec) provide basal glycemic control.

The most common and dangerous adverse effect across all insulin types is hypoglycemia.

When mixing, always draw up clear (Regular/Rapid) before cloudy (NPH).

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