Pathophysiology Of Thyroid Dysfunction( Chemical Pathology)

Question 1

What tests are used for thyroid function? And how do we diagnose based on them?(3)

Answer 1

1.Testing for TSH levels:
• It is decreased in hyperthyroidism.
• It is increased in hypothyroidism.
2. Total T3 and T4
3. Free T3 and T4

Question 2

Major binding protein for T3 and T4

Answer 2

Thyroxine binding globulin

Question 3

Most abundant binding protein for T3 and T4

Answer 3

Albumin

Question 4

What are some of the causes of low TSH in clinically euthyroid patients?

Answer 4

Pregnancy
Subclinical hyperthyroidism
Treated hyperthyroidism( first 6 months)
Ophthalmic grave’s disease
Nonthyroidal illness
Treatment with dopaminergic drugs or high dose glococorticoids

Question 5

What are causes of high TSH in some clinically euthyroid patients?(2)

Answer 5

Subclinical hypothyroidism
Recovery phase of nonthyroidal illness

Question 6

Causes of hyperthyroidism, define the terms(5)

Answer 6

•Graves disease- autoimmune, TSH receptor stimulating antibodies.
•Trophoblastic- Secretion of high hCG which mimics the effects of TSH.
•Fractitious- Exogenous administration of T4.
•Iodine-induced
•Thyroiditis:-Transient phenomenon resulting from release of stored T4 from damaged thyroid gland.

Question 7

How can we manage hyperthyroidism(NB)

Answer 7

Carbimazole
Radioiodine
Thyroidectomy

Question 8

What provides the best indicator for thyroid status in the early months of hyperthyroidism treatment?

Answer 8

Free T4

Question 9

What are some of the causes of hypothyroidism?

Answer 9

IATROGENIC:
-Radioactive iodine
-Thyroidectomy
CONGENITAL:
-Iodine deficiency
SECONDARY
-Hypopituitarism
-Hypothalamic dysfunction
Hashimoto’s thyroiditis
Atrophic thyroiditis
Post-partum thyroiditis

Question 10

Management of hypothyroidism(NB)

Answer 10

T4 replacement therapy

Question 11

What is the condition for replacing T4 in subclinical hypothyroidism

Answer 11

TSH>10mu/L

Question 12

When are Thyroid Function Tests(TFT) unreliable?(4)

Answer 12

-Nonthyroidal illness
- Neonate
- Pregnancy
- Recovery from illness

Question 13

What are the tests affected by hyperthyroidism?(4)

Answer 13

Hyperglycaemia
Hypocholesterolaemia
Abnormal liver function test
Hypercalcaemia

Question 14

What are the tests affected by hypothyroidism?(3)

Answer 14

Hyponatraemia
Hypercholesterolaemia
Hyperprolactinaemia

Question 15

What causes abnormal results ( hypothyroidism) in euthyroid patients?(3)

Answer 15

Abnormal Thyroxine Binding Globulin.
Genetic variants of albumin and pre-albumin.
Assay interference

Question 16

What are other tests than can be taken for hypothyroidism?(3)

Answer 16

Thyroid-Releasing Hormone test
AntiTPO
TRAbs