Examkin

Question

Difficulty: EasyEndocrinology and Metabolism

A 55-year-old woman comes to the clinic for a routine health maintenance examination. She reports mild fatigue over the last few months but attributes it to her busy work schedule. She denies any weight changes, cold intolerance, constipation, or changes in her skin and hair. Her medical history is unremarkable, and she takes no medications. Vital signs are within normal limits. Physical examination reveals a normal-appearing, non-tender thyroid gland with no palpable nodules. Laboratory studies show:

Serum thyroid-stimulating hormone (TSH): 8.5 μU/mL8.5 \text{ } \mu\text{U/mL} (Normal: 0.4−4.0 μU/mL0.4 - 4.0 \text{ } \mu\text{U/mL})
Serum free thyroxine (T4): 1.3 ng/dL1.3 \text{ ng/dL} (Normal: 0.9−1.7 ng/dL0.9 - 1.7 \text{ ng/dL})

Which of the following is the most likely diagnosis?

  1. Subclinical hypothyroidismAnswer
  2. B
    Overt primary hypothyroidism
  3. C
    Secondary hypothyroidism
  4. D
    Euthyroid sick syndrome
  5. E
    Central hyperthyroidism

Answer

Subclinical hypothyroidism
The correct diagnosis is subclinical hypothyroidism. This condition is defined biochemically by an elevated serum TSH concentration in the setting of normal serum free T4 and T3 concentrations. Patients are typically asymptomatic, though some may report mild, non-specific symptoms such as fatigue. In contrast, overt hypothyroidism requires a low free T4 level.

Step-by-Step Solution

1
Evaluate the patient's symptoms and clinical context.
The patient is generally healthy and asymptomatic aside from mild fatigue.
Establishing the clinical status helps differentiate overt thyroid disease from subclinical or alternative diagnoses.
2
Interpret the serum TSH level.
TSH is elevated at 8.5 μU/mL.
An elevated TSH indicates that the pituitary gland is attempting to stimulate the thyroid, typically because thyroid hormone levels are insufficient.
3
Interpret the serum free T4 level.
Free T4 is normal at 1.3 ng/dL.
The free T4 level determines whether the hypothyroidism is overt (low free T4) or subclinical (normal free T4).
4
Synthesize the findings to make a diagnosis.
The combination of elevated TSH and normal free T4 points strictly to subclinical hypothyroidism.
This specific laboratory pattern defines subclinical hypothyroidism, regardless of the presence of mild non-specific symptoms like fatigue.

Key Concept

Diagnosis of subclinical hypothyroidism
Estimated Time:45s
Rate this question

Topics

Endocrinology and Metabolism

More questions from this topic