Thyroid Diseases Flashcards
What are the 3 general roles of thyroid hormones?
control of metabolism
regulation of growth
multiple roles in development
Describe the HPT axis, including negative feedback
Hypothalamus releases TRH
Pituitary releease TSH
Thyroid releases T3 and T4
Both T3 and T4 feedback to reduce TRH and TSH release
Thyroid hormone synthesis:
- Which cells produce it?
- What is the precursor?
- Which enzyme binds iodine to tyrosine residues?
- Which is the active form?
- How is the inactive form converted to the active form and where?
- follicular thyroid cells
- thyroglobulin
- thyroperoxidase
- T3
- By deiodinase enzymes present in the peripheral tissues
Describe thyroid hormone synthesis in 5 steps
- TSH binds to TSHR
- I- uptake by NIS
- Iodine of tyrosine residues by thryroperoxidase (TPO)
- Coupling of iodotyrosyl residues by TPO
- Export of mature Tg to colloid where it is stored
What are the names of T3 and T4
T3 = triiodothyronine T4 = thyroxine
In terms of serum TSH, free T4 and free T3, what are results of thyroid function tests and hyperthyroidism and hypothyroidism?
Hyperthyroidism: - low TSH - high T4 - high T3 Hypothyroidism - high TSH - low T4 - low T3
What are some of the signs and symptoms of hyperthyroidism?
tachycardia weight loss diarrhoea tremor anxiety sore, gritty eyes double vision staring eyes sensitive to heat
What is graves disease an autoimmune disorder to?
TSH receptor
What are the extra-thyroidal manifestation of Grave’s disease?
Eyes -lid lag/retraction - proptosis (bulging) - periorbital puffiness - conjuctival oedema Skin - pretibial myxoedema
When does neonatal hyperthyroidism occur?
TSH-R antibodies from mother cross the placenta
What is the group of drugs used to treat hyperthyroidism called? What is their mechanism of action?
Give an example
What is a serious side effect?
thionamides, inhibit thyroperoxidase
carbimazole
agranulocytosis
What are the 3 treatment option of hyperthyroidism?
antithyroid drugs
thyroidectomy
radioiodine therapy (iodine131)
What are the complications of a total thyroidectomy?
hypothyroidism hypoparathyroidism recurrent laryngeal nerve damage bleeding thyroid storm
What are the possible causes of hypothyroidism?
autoimmune e.g. Hashimoto's after thyroidectomy silent/subacute iodine deficiency congenital
What are some signs and symptoms of hypothyroidism?
bradycardia weight gain constipation cold intolerance carpal tunnel depression vitiligo
