Laboratory Diagnosis of Thyroid Disorders

Question 1

A patient with apparent symptoms of hypothyroidism. What laboratory tests would be the
most appropriate to perform?

Answer 1

Features of Hypothyroidism:

1) decrease BMR (cold)
2) slower bowel movement
3) Bradycardia
4) gain weight
5) Mentally slow
6) Hair loss

Tests:

-simultaneously measure FT3, FT4 and TSH

IF LOW TSH (2ndary or tertiary)
>Inject TRH and see how pituitary

IF HIGH TSH (primary hypofunction)

Question 2

A 40 year old woman seeks evaluation for subfebrility and diarrhea commenced 2–3 weeks before.
Blood glucose: 6.6 mmol/l. Blood pressure: 160/85 mmHg, heart rate: 120/min. Serum TSH: 0.15 mU/l (decreased), FT4: 60 pmol/l (elevated), TRAb titer
elevated, TPO-antibody positive.
What is the most likely diagnosis? What other test would you order to specify your
diagnosis?

Answer 2

Clinical findings:
-subfebrility and diahorrhea, HT, Tachycardia

Lab Findings:

• blood glucose shows Impaired fasting glucose (test again)
• FT4 is very high (indicating hyperactivity of thyroid)
• Thyroid stimulating AB and TPO indicate HSR 2 -> autoimmune

Conclusion:
-high T4 due to autoactivation of TSH-R. The low TSH due to negative feedback.
THIS IS GRAVES DISEASE (continous stimulation of thyroid -> diffuse goiter)

Tests:
no need
-US
-Scintography

Question 3

Normal Parameters

Answer 3

Blood glucose: 3-6mM
Serum TSH: 0.3-6 mU/ml
free T4: 10-29 pM

Question 4

A 42 year old woman developed diffusely enlarged, painless thyroid glands. Total T4 is
decreased, thyroid uptake of radioiodine is low. ECG reveals low voltage and
bradycardia. The thyroid autoimmunity panel demonstrates the presence of TgAb and
TPO-Ab. What is the most likely diagnosis? Is this condition characterized by a hypo or
hyperfunction of the thyroid gland?

Answer 4

Clinical findings:
-enlarged painless thyroid gland
-low voltage and bradycardia
THIS IS HYPOTHYROIDISM

Lab findings:

• decrease T4 indicate Hypothyroidism
• Presence of TGAB and TPO ->autoimmune

Conclusion:
-hypothyroidism caused by Hashimoto thyroidotis
AT BEGINNING HYPERTHYR THEN HYPO

Question 5

A schoolgirl at the age of 14 without any complaints develops diffusely enlarged painless
thyroid glands recognized accidentally by the school doctor.
Laboratory findings: FT4 is slightly decreased, whereas total T3 is slightly elevated. Thyroid uptake of radioiodine is increased. FT4 gets normalized after treatment with anorganic iodine.
What is the most likely diagnosis? Try to interpret the opposite changes in hormone
levels.

Answer 5

The decrease FT4 increases with iodine (indicating normal function of thyroid gland)

Patient had iodine deficiency -> w/o iodine cannot produce thyroid hormones so no inhibits TSH -> so TSH overstimulate to produce TH causing Goiter

More T3 as it has 1 less iodine and is more potent

Iodine Deficiency:

• > in less developed countries
• > Puberty/pregnancy

Question 6

An 11 month old baby with protruded belly and retarded in movement development has been brought for medical evaluation. Serum FT4 and FT3 are decreased. Serum MIT/DIT
are elevated and their urinary excretion increased.
What is the most likely diagnosis?

Answer 6

clinical signs:
-protruded belly and retarded movement development -> signs of Hypothyroidism

Lab findings:
-decrease Ft4 says hypothyroidism

Conclusion

• enzyme deficiency in conjugation of MIT AND DIT
• strong chance it develops to mental retardation so screen at birth

Question 7

List those thyroid tests that are considered helpful in the diagnosis of thyroid cancer!

Answer 7

1) Fine Needle Biopsy (histiological)
2)Radioactive scintography
I-131 -> for whole body scan to see metastatized of thyroid cancer

3)Thyroid US
(to distinguish from solid and cystic-seldom malignant

4) Measure Serum Ca2+ and Calcitonon levels:
- if hypocalcemia and high calcitonin -> medullary thyroid cancer

5) Tumour markers for thyroid cancer
6) Measure [TG] in plasma