AANP Family Nurse Practitioner (FNP) Certification ExamDiagnosisMedium
A 45-year-old female presents with fatigue, constipation, cold intolerance, and weight gain despite no changes in diet. On examination, her skin is dry, and she has bradycardia. Her thyroid-stimulating hormone (TSH) level is 12.5 mIU/L (normal range 0.4-4.0 mIU/L), and free T4 is low. What is the most likely diagnosis?
- AHyperthyroidism
- BSubclinical hypothyroidism
- CSecondary hypothyroidism
- DPrimary hypothyroidism
Show answer & explanationAnswer & explanation
Correct answer: D. Primary hypothyroidism
The patient's symptoms (fatigue, constipation, cold intolerance, weight gain, dry skin, bradycardia) combined with a high TSH and low free T4 are classic indicators of primary hypothyroidism.
Why the other options are wrong
- A. Hyperthyroidism would present with opposite symptoms (e.g., weight loss, heat intolerance, tachycardia) and low TSH with high T4.
- B. Subclinical hypothyroidism involves an elevated TSH but normal free T4 levels, which is not the case here.
- C. Secondary hypothyroidism involves a low TSH and low free T4, indicating a pituitary problem, which is inconsistent with the high TSH found.
Primary Hypothyroidism
A condition in which the thyroid gland is unable to produce sufficient thyroid hormones, leading to an elevated TSH and low free T4.
- Symptoms: fatigue, weight gain, cold intolerance, constipation, dry skin, bradycardia.
- Labs: High TSH, Low Free T4.
- Common cause: Hashimoto's thyroiditis.
Memory trick: Too much TSH means the thyroid is 'Screaming' for more T4.