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☕️ Which of the following is the most likely underlying mechanism for the elevated cholesterol in this patient?
Morning Quiz 130 ☕️
Dr. Shoaib Ahmad Baig
August 14, 2025
Morning Quiz ☕️
A 67-year-old man presents to the office due to increased fatigue and weight gain over the past 6 months.
Medical History
Hypertension: Controlled with a calcium channel blocker.
Previous evaluation (2 years ago):
Physical examination was unremarkable.
Blood tests (including lipid panel) were normal.
Current Findings
Vitals:
Blood pressure: 135/98 mm Hg
Pulse: 62/min
BMI: 28 kg/m²
Physical Exam:
Thyroid is mildly enlarged, irregular, and firm in consistency.
Laboratory Results:
Elevated TSH
Low free thyroxine (T4)
High total and LDL cholesterol
Mildly elevated triglycerides
Question
Which of the following is the most likely underlying mechanism for the elevated cholesterol in this patient?
Answer Choices
A. Activation of transcription factor peroxisome proliferator-activated receptor alpha
B. Decreased LDL receptor gene expression
C. Increased lipoprotein lipase gene expression
D. Induction of HMG-CoA reductase
E. Upregulation of LDL receptor degradation
Correct Answer 🎯: B. Decreased LDL receptor gene expression
⚙️
↓ Thyroid hormone (T4)
⬇
↓ Metabolic rate
⬇
Fatigue + Weight gain + Bradycardia (Pulse 62/min)
⬇
↓ Lipid metabolism
⬇
↓ LDL receptor synthesis in liver
⬇
↓ LDL clearance from plasma
⬇
↑ Total + LDL cholesterol
⬇
↓ Lipoprotein lipase activity
⬇
↓ Triglyceride clearance
⬇
Mild ↑ Triglycerides
⬇
Thyroid enlargement (firm, irregular)
⬇
Suggests chronic autoimmune thyroiditis (Hashimoto’s)
⬇
Chronic lymphocytic infiltration → Fibrosis
⬇
↓ T4 → ↑ TSH (due to loss of feedback)
Differential Table ⚖️
Differential | Mechanism | Why Incorrect? |
|---|---|---|
Activation of PPAR-α | ↑ PPAR-α → ↑ β-oxidation + ↑ LPL → ↓ TG + ↓ LDL | Seen in fibrate therapy; does not raise LDL |
↑ Lipoprotein lipase gene expression | ↑ LPL → ↑ TG clearance ⚙ → ↓ TG | Hypothyroid patients have ↓ LPL = opposite effect |
Induction of HMG-CoA reductase | ↑ HMG-CoA reductase ⚙ → ↑ Cholesterol synthesis | Metabolic rate is ↓ in hypothyroidism = enzyme activity drops |
↑ LDL receptor degradation | ↑ PCSK9 → Tags LDL receptor for destruction → ↓ LDL clearance | Not relevant here; no PCSK9 role in hypothyroidism |
Visual Cheat Chart 📈
Practice Questions ⏳️
Most importantly solve Uworld With Question IDs:
983, 14985, 20306, 770, 12512, 769, 20366, 14951, 20204
Stay Hungry, Stay Curious!
Your Brother in This Struggle
Dr. Shoaib Ahmad
