Pathophysiology Of Thyroid Dysfunction( Chemical Pathology) Flashcards
What tests are used for thyroid function? And how do we diagnose based on them?(3)
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
Major binding protein for T3 and T4
Thyroxine binding globulin
Most abundant binding protein for T3 and T4
Albumin
What are some of the causes of low TSH in clinically euthyroid patients?
Pregnancy
Subclinical hyperthyroidism
Treated hyperthyroidism( first 6 months)
Ophthalmic grave’s disease
Nonthyroidal illness
Treatment with dopaminergic drugs or high dose glococorticoids
What are causes of high TSH in some clinically euthyroid patients?(2)
Subclinical hypothyroidism
Recovery phase of nonthyroidal illness
Causes of hyperthyroidism, define the terms(5)
•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.
How can we manage hyperthyroidism(NB)
Carbimazole
Radioiodine
Thyroidectomy
What provides the best indicator for thyroid status in the early months of hyperthyroidism treatment?
Free T4
What are some of the causes of hypothyroidism?
IATROGENIC:
-Radioactive iodine
-Thyroidectomy
CONGENITAL:
-Iodine deficiency
SECONDARY
-Hypopituitarism
-Hypothalamic dysfunction
Hashimoto’s thyroiditis
Atrophic thyroiditis
Post-partum thyroiditis
Management of hypothyroidism(NB)
T4 replacement therapy
What is the condition for replacing T4 in subclinical hypothyroidism
TSH>10mu/L
When are Thyroid Function Tests(TFT) unreliable?(4)
-Nonthyroidal illness
- Neonate
- Pregnancy
- Recovery from illness
What are the tests affected by hyperthyroidism?(4)
Hyperglycaemia
Hypocholesterolaemia
Abnormal liver function test
Hypercalcaemia
What are the tests affected by hypothyroidism?(3)
Hyponatraemia
Hypercholesterolaemia
Hyperprolactinaemia
What causes abnormal results ( hypothyroidism) in euthyroid patients?(3)
Abnormal Thyroxine Binding Globulin.
Genetic variants of albumin and pre-albumin.
Assay interference