Question 35

Note: Questions 35 - 37 share the same answer choices.


Match the patient with the thyroid function testing results that would help diagnose her condition.


A 33 yo G1P1 with 40-day cycles who has dry skin and constantly feels tired. She is trying to become pregnant but has difficulty interpreting her ovulation predictor kit.

Answer Choices:

Elevated thyroid stimulating hormone (TSH) level and normal free thyroxine (T4) level

Low TSH with elevated free T4 with thyroid antibodies

High TSH and low free T4

Low TSH, normal free T4, normal triiodothyronine (T3) level

Correct Answer:

High TSH and low free T4

Explanation:

  • Free T4 is controlled by the pituitary hormone TSH

  • T4 and T3 circulate bound and unbound to binding proteins. The unbound (free T4 and free T3) is what exerts effects on target tissues.

  • Thyroid antibody tests for antithyroid peroxidase and antithyroglobuin can help determine the etiology of thyroid dysfunction.

  • Signs and symptoms of hypothyroidism include dry skin, cold sensitivity, fatigue, muscle cramps, constipation and menstrual irregularities. High TSH and low free T4 confirms the diagnosis.

  • Subclinical hypothyroidism occurs before signs and symptoms present. Labs show elevated TSH and normal free T4. Around 2-4% of cases progress to overt hypothyroidism each year.

  • Graves disease is most common cause of hyperthyroidism. This is an autoimmune disorder with thyroid antibody stimulation of the TSH receptor which leads to increased release of thyroid hormone with growth of the thyroid gland. Symptoms can include heat intolerance, diarrhea, weight loss, palpitations, sweating, lid lag, hyperreflexia, tachycardia and tremor. Menstrual irregularities can vary. Labs show low TSH and elevated free R4 with thyroid antibodies.