A 31-year-old woman has palpitations, anxiety and weight loss 3 months after delivering a healthy baby, whom she is breastfeeding. She has a small painless goiter and no eye signs. Results: TSH < 0.01 mIU/L (0.4-4.0); free T4 2.6 ng/dL [33 pmol/L] (0.8-1.8 [10-23]); total T3 210 ng/dL [3.2 nmol/L] (80-200 [1.2-3.1]); thyroid peroxidase antibody strongly positive; TSH receptor antibody negative; thyroglobulin raised; ESR 12 mm/h. She takes no thyroid medicine, and her thyroid tests were normal early in the pregnancy. The most likely diagnosis is:

Postpartum (painless) thyroiditis

Hidden intake of thyroid hormone

Subacute granulomatous thyroiditis

A 59-year-old man is seen 2 weeks after discharge from a 10-day ICU stay for septic shock, during which he received a dopamine infusion. In the ICU his TSH was 0.2 mIU/L, with free T4 0.9 ng/dL [12 pmol/L] and a low total T3. He now feels well and takes no thyroid drugs. Today: TSH 8.6 mIU/L (0.4-4.0); free T4 0.9 ng/dL [12 pmol/L] (0.8-1.8 [10-23]); total T3 92 ng/dL [1.4 nmol/L] (80-200 [1.2-3.1]). Thyroid peroxidase antibody is negative, and his TSH 6 months ago was 1.9 mIU/L. What are the best interpretation and next step?

Recovery from illness; repeat tests in 4-6 weeks

Primary hypothyroidism; start levothyroxine

Assay interference; retest by another method

Central hypothyroidism; assess the pituitary

A woman with Graves disease has taken methimazole for 6 weeks and feels better. Free T4 is now 1.1 ng/dL [14 pmol/L] (0.8-1.8 [10-23]), but TSH is still < 0.01 mIU/L (0.4-4.0). The best interpretation is:

TSH recovery lags; follow free T4 and T3

She now has central hypothyroidism

The TSH reflects biotin interference

Treatment has failed; increase the dose

A healthy term newborn's screening sample, collected at 6 hours of age, shows a TSH just above the program's cutoff. What is the best interpretation and action?

Postnatal TSH surge; repeat the screen

Central hypothyroidism; measure free T4 only

Congenital hypothyroidism; start levothyroxine

Maternal TSH transfer; test the mother

Endocrinology: interpretation - thyroid

17 ASCP MLS practice questions on Endocrinology: interpretation - thyroid, part of Chemistry. The first 17 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 31-year-old woman has palpitations, anxiety and weight loss 3 months after delivering a healthy baby, whom she is breastfeeding. She has a small painless goiter and no eye signs. Results: TSH < 0.01 mIU/L (0.4-4.0); free T4 2.6 ng/dL [33 pmol/L] (0.8-1.8 [10-23]); total T3 210 ng/dL [3.2 nmol/L] (80-200 [1.2-3.1]); thyroid peroxidase antibody strongly positive; TSH receptor antibody negative; thyroglobulin raised; ESR 12 mm/h. She takes no thyroid medicine, and her thyroid tests were normal early in the pregnancy. The most likely diagnosis is:
1. AHidden intake of thyroid hormone
2. BPostpartum (painless) thyroiditis
3. CSubacute granulomatous thyroiditis
4. DGraves disease after pregnancy
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Answer: B · Postpartum (painless) thyroiditis
Thyrotoxicosis within a year of delivery in a woman with positive TPO antibodies is typical of postpartum thyroiditis, an autoimmune destructive thyroiditis. Stored hormone leaks from damaged follicles, so free T4 rises more than T3 and thyroglobulin is raised. A negative TSH receptor antibody makes Graves disease unlikely, and Graves usually gives a T3-predominant pattern. The painless gland and normal ESR argue against subacute granulomatous thyroiditis, and a raised thyroglobulin excludes hidden thyroid hormone intake, which suppresses it. The thyrotoxic phase often gives way to a hypothyroid phase, so TSH should be followed for the rest of the first postpartum year.
- A: Taking thyroid hormone suppresses thyroglobulin, but here it is raised.
- C: Subacute granulomatous thyroiditis is painful and raises the ESR.
- D: TSH receptor antibody is negative, and Graves usually gives a T3-predominant pattern.
Question 2 · Hard
A 59-year-old man is seen 2 weeks after discharge from a 10-day ICU stay for septic shock, during which he received a dopamine infusion. In the ICU his TSH was 0.2 mIU/L, with free T4 0.9 ng/dL [12 pmol/L] and a low total T3. He now feels well and takes no thyroid drugs. Today: TSH 8.6 mIU/L (0.4-4.0); free T4 0.9 ng/dL [12 pmol/L] (0.8-1.8 [10-23]); total T3 92 ng/dL [1.4 nmol/L] (80-200 [1.2-3.1]). Thyroid peroxidase antibody is negative, and his TSH 6 months ago was 1.9 mIU/L. What are the best interpretation and next step?
1. APrimary hypothyroidism; start levothyroxine
2. BAssay interference; retest by another method
3. CRecovery from illness; repeat tests in 4-6 weeks
4. DCentral hypothyroidism; assess the pituitary
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Answer: C · Recovery from illness; repeat tests in 4-6 weeks
During severe illness, and with dopamine or glucocorticoids, TSH secretion is suppressed and T3 falls; this was his ICU pattern. As the patient recovers, TSH rebounds and can rise above the reference range for some weeks while free T4 returns to normal, so a mildly raised TSH soon after discharge is expected. His normal TSH 6 months ago, negative TPO antibody, normal free T4 and recovering T3 all fit this better than new primary hypothyroidism. Thyroid tests should be repeated in about 4-6 weeks, with treatment considered only if TSH stays high. Central hypothyroidism would not produce a raised TSH, and nothing here suggests assay interference.
- A: Starting levothyroxine now would treat a passing rise; TPO antibody is negative and free T4 normal.
- B: The results follow the known course of recovery, so a second method is not needed first.
- D: Central hypothyroidism gives a low or normal TSH, not a rising one.
Question 3 · Hard
A woman with Graves disease has taken methimazole for 6 weeks and feels better. Free T4 is now 1.1 ng/dL [14 pmol/L] (0.8-1.8 [10-23]), but TSH is still < 0.01 mIU/L (0.4-4.0). The best interpretation is:
1. AShe now has central hypothyroidism
2. BThe TSH reflects biotin interference
3. CTSH recovery lags; follow free T4 and T3
4. DTreatment has failed; increase the dose
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Answer: C · TSH recovery lags; follow free T4 and T3
After months of hyperthyroidism, the pituitary thyrotrophs are suppressed and can take weeks to months to recover, even after free T4 returns to normal. During this time TSH stays low and does not reflect the current thyroid state. Dose changes are guided by free T4 and T3 until TSH recovers. Increasing the dose on the basis of TSH alone risks making her hypothyroid.
- A: Central hypothyroidism would give a low free T4.
- B: Nothing suggests biotin use, and the low TSH has an expected cause.
- D: A normal free T4 shows the treatment is working.
Question 4 · Hard
A healthy term newborn's screening sample, collected at 6 hours of age, shows a TSH just above the program's cutoff. What is the best interpretation and action?
1. APostnatal TSH surge; repeat the screen
2. BCentral hypothyroidism; measure free T4 only
3. CCongenital hypothyroidism; start levothyroxine
4. DMaternal TSH transfer; test the mother
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Answer: A · Postnatal TSH surge; repeat the screen
TSH rises sharply within minutes of birth, peaks within about the first hour and then falls over the next 2 to 3 days. A sample taken before 24 hours can therefore show a raised TSH in a healthy baby. Screening programs ask for collection at 24 to 48 hours of age and repeat early samples. A clearly high TSH on a properly timed sample is followed at once by serum TSH and free T4, and treatment starts promptly if confirmed.
- B: Central hypothyroidism gives a low or normal TSH, not a raised one.
- C: A marginal TSH in the first hours of life is expected and does not diagnose congenital hypothyroidism.
- D: Maternal TSH does not cross the placenta.
Question 5 · Medium
A patient in intensive care with sepsis has TSH 0.3 mIU/L (0.4-4.0), free T4 0.9 ng/dL [12 pmol/L] (0.8-1.8 [10-23]), total T3 60 ng/dL [0.9 nmol/L] (80-200 [1.2-3.1]) and a high reverse T3. What is the most likely explanation?
1. APrimary hypothyroidism
2. BCentral hypothyroidism
3. CNonthyroidal illness
4. DSubclinical hyperthyroidism
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Answer: C · Nonthyroidal illness
In severe illness, type 1 deiodinase activity falls, so less T4 is converted to T3 and less reverse T3 is cleared. T3 drops and reverse T3 rises, while TSH may be low-normal or slightly low, partly from cytokines and drugs such as dopamine and glucocorticoids. These changes are an adaptation, not thyroid disease, so thyroid tests in ICU patients are best avoided unless thyroid disease is suspected. TSH may rise transiently during recovery.
- A: Primary hypothyroidism raises TSH.
- B: Central hypothyroidism would not raise reverse T3, and free T4 here is still normal.
- D: Subclinical hyperthyroidism has a normal T3, not a low one.
Question 6 · Hard
A 40-year-old man has heat intolerance and headaches. TSH 5.8 mIU/L (0.4-4.0), free T4 3.0 ng/dL [39 pmol/L] (0.8-1.8 [10-23]), raised alpha subunit, and a pituitary mass on MRI. What is the most likely diagnosis?
1. ATSH-secreting adenoma
2. BIncreased TBG
3. CGraves disease
4. DThyroid hormone resistance
Answer and explanation in LearnFree account
Question 7 · Easy
TSH is the preferred first test of thyroid function in outpatients mainly because:
1. ATSH has no daily variation in its secretion
2. BTSH assays are free of antibody interference
3. CSmall free T4 changes cause large TSH changes
4. DTSH is unaffected by any pituitary disease
Answer and explanation in LearnFree account
Question 8 · Hard
Three months after starting amiodarone, a clinically euthyroid man has free T4 2.1 ng/dL [27 pmol/L] (0.8-1.8 [10-23]), total T3 85 ng/dL [1.3 nmol/L] (80-200 [1.2-3.1]), a high reverse T3 and TSH 3.2 mIU/L (0.4-4.0). How are these results best interpreted?
1. AAmiodarone-induced hypothyroidism
2. BTSH-secreting pituitary adenoma
3. CAmiodarone-induced thyrotoxicosis
4. DExpected effect on T4 deiodination
Answer and explanation in LearnFree account
Question 9 · Medium
Results: free T4 0.5 ng/dL [6 pmol/L] (0.8-1.8 [10-23]); TSH 1.1 mIU/L (0.4-4.0). These results point to:
1. APrimary hypothyroidism
2. BSubclinical hypothyroidism
3. CCentral hypothyroidism
4. DThyroid hormone resistance
Answer and explanation in LearnFree account
Question 10 · Hard
A 30-year-old woman has palpitations and weight loss, with no goiter and no neck pain. TSH < 0.01 mIU/L (0.4-4.0), free T4 2.8 ng/dL [36 pmol/L] (0.8-1.8 [10-23]), thyroglobulin undetectable, TSH receptor antibody negative. The most likely cause is:
1. AToxic adenoma
2. BPainless (silent) thyroiditis
3. CGraves disease
4. DLevothyroxine ingestion
Answer and explanation in LearnFree account
Question 11 · Medium
A patient with primary hypothyroidism has a levothyroxine dose increase. The new dose is best checked by measuring:
1. ATSH, 6 to 8 weeks after the change
2. BTotal T3, 1 week after the change
3. CFree T4, 2 days after the change
4. DThyroglobulin, 1 month after the change
Answer and explanation in LearnFree account
Question 12 · Easy
Subclinical hypothyroidism is defined by which result pattern?
1. ANormal TSH, low free T4
2. BSuppressed TSH, normal free T4
3. CRaised TSH, low free T4
4. DRaised TSH, normal free T4
Answer and explanation in LearnFree account
Question 13 · Medium
Results: TSH < 0.01 mIU/L (0.4-4.0); free T4 1.5 ng/dL [19 pmol/L] (0.8-1.8 [10-23]); total T3 320 ng/dL [4.9 nmol/L] (80-200 [1.2-3.1]). What is this pattern called?
1. ANonthyroidal illness
2. BSubclinical hyperthyroidism
3. CCentral hyperthyroidism
4. DT3 thyrotoxicosis
Answer and explanation in LearnFree account
Question 14 · Medium
Results: total T4 15.0 µg/dL [193 nmol/L] (5.0-12.0 [64-154]); free T4 1.3 ng/dL [17 pmol/L] (0.8-1.8 [10-23]); TSH 2.1 mIU/L (0.4-4.0). Which condition best explains them?
1. ATSH-secreting adenoma
2. BIncreased TBG
3. CEarly Graves disease
4. DThyroid hormone resistance
Answer and explanation in LearnFree account
Question 15 · Hard
At 10 weeks of pregnancy, a woman with severe vomiting has TSH 0.05 mIU/L (0.4-4.0), free T4 2.0 ng/dL [26 pmol/L] (nonpregnant 0.8-1.8 [10-23]), a negative TSH receptor antibody and no goiter. What is the most likely cause?
1. AGraves disease
2. BhCG acting on the TSH receptor
3. CToxic multinodular goiter
4. DExcess thyroxine-binding globulin
Answer and explanation in LearnFree account
Question 16 · Medium
A 44-year-old woman had the thyroid results shown over 30 weeks, without any thyroid medication or other treatment. Which condition best explains the sequence?
Figure: MedExams
1. ATSH-secreting pituitary adenoma
2. BGraves disease
3. CDestructive thyroiditis
4. DToxic multinodular goiter
Answer and explanation in LearnFree account
Question 17 · Medium
A high TSH with a low free T4 indicates which condition?
1. APrimary hypothyroidism
2. BPrimary hyperthyroidism
3. CEuthyroid sick syndrome
4. DSecondary (pituitary) hypothyroidism
Answer and explanation in LearnFree account

Endocrinology: interpretation - thyroid

A woman with Graves disease has taken methimazole for 6 weeks and feels better. Free T4 is now 1.1 ng/dL [14 pmol/L] (0.8-1.8 [10-23]), but TSH is still < 0.01 mIU/L (0.4-4.0). The best interpretation is:

A healthy term newborn's screening sample, collected at 6 hours of age, shows a TSH just above the program's cutoff. What is the best interpretation and action?

A patient in intensive care with sepsis has TSH 0.3 mIU/L (0.4-4.0), free T4 0.9 ng/dL [12 pmol/L] (0.8-1.8 [10-23]), total T3 60 ng/dL [0.9 nmol/L] (80-200 [1.2-3.1]) and a high reverse T3. What is the most likely explanation?

A 40-year-old man has heat intolerance and headaches. TSH 5.8 mIU/L (0.4-4.0), free T4 3.0 ng/dL [39 pmol/L] (0.8-1.8 [10-23]), raised alpha subunit, and a pituitary mass on MRI. What is the most likely diagnosis?

TSH is the preferred first test of thyroid function in outpatients mainly because:

Three months after starting amiodarone, a clinically euthyroid man has free T4 2.1 ng/dL [27 pmol/L] (0.8-1.8 [10-23]), total T3 85 ng/dL [1.3 nmol/L] (80-200 [1.2-3.1]), a high reverse T3 and TSH 3.2 mIU/L (0.4-4.0). How are these results best interpreted?

Results: free T4 0.5 ng/dL [6 pmol/L] (0.8-1.8 [10-23]); TSH 1.1 mIU/L (0.4-4.0). These results point to:

A 30-year-old woman has palpitations and weight loss, with no goiter and no neck pain. TSH < 0.01 mIU/L (0.4-4.0), free T4 2.8 ng/dL [36 pmol/L] (0.8-1.8 [10-23]), thyroglobulin undetectable, TSH receptor antibody negative. The most likely cause is:

A patient with primary hypothyroidism has a levothyroxine dose increase. The new dose is best checked by measuring:

Subclinical hypothyroidism is defined by which result pattern?

Results: TSH < 0.01 mIU/L (0.4-4.0); free T4 1.5 ng/dL [19 pmol/L] (0.8-1.8 [10-23]); total T3 320 ng/dL [4.9 nmol/L] (80-200 [1.2-3.1]). What is this pattern called?

Results: total T4 15.0 µg/dL [193 nmol/L] (5.0-12.0 [64-154]); free T4 1.3 ng/dL [17 pmol/L] (0.8-1.8 [10-23]); TSH 2.1 mIU/L (0.4-4.0). Which condition best explains them?

At 10 weeks of pregnancy, a woman with severe vomiting has TSH 0.05 mIU/L (0.4-4.0), free T4 2.0 ng/dL [26 pmol/L] (nonpregnant 0.8-1.8 [10-23]), a negative TSH receptor antibody and no goiter. What is the most likely cause?

A 44-year-old woman had the thyroid results shown over 30 weeks, without any thyroid medication or other treatment. Which condition best explains the sequence?

A high TSH with a low free T4 indicates which condition?