L7 Thyroid Hormones 2 Flashcards
Toxic multinodular goitre usually occurs in…
older patients with longstanding euthyroid multinodular goitre
Presentations of toxic multinodular goitre
- tachycardia, heart failure or arrhythmia
- sometimes weight loss, nervousness, weakness, tremors & sweats
Laboratory findings of toxic multinodular goitre
suppressed TSH, elevated serum T3 levels, less striking elevation of serum T4
Toxic multinodular goitre management
- control of the hyperthyroid state with anti-thyroid drugs, followed by radioiodine (therapy of choice)
- if goitre is very large, thyroidectomy is considered if patient is a good surgical candidate
What is amiodarone?
an anti-arrhythmic drug that contains 37.3% iodine by weight
Two types of amiodarone-induced thryotoxicosis
Type 1: thyrotoxicosis due to excess iodine
Type 2: amiodarone-induced thyroiditis, with inflammation and release of stored hormone into the bloodstream, causing thyrotoxicosis
Which type of AIT typically develops after more prolonged amiodarone use?
Type 2 - thyroiditis
Treatment for AIT
- iodine-induced thyrotoxicosis can be controlled with methimazole/carbimazole and beta blockers
- treatment with potassium perchlorate to block further iodine uptake requires careful monitoring because it has been associated with pernicious anaemia
- prednisone therapy for drug-induced thyroiditis
- mixed form of disease is treated with both thioamides and prednisone
- total thyroidectomy is curative - may be needed in patients who are non-responsive to pharmacologic therapy
What is non-toxic goitre?
Goitre not associated with hyperthyroidism, can be diffuse or nodular
What is the most common cause of non-toxic goitre?
Iodine deficiency
Development of NTG in patients with impaired hormone synthesis or severe iodine deficiency causes an increase in __ secretion.
TSH
TSH-induced diffuse thyroid hyperplasia causes…
focal hyperplasia with necrosis and haemorrhage, and development of new areas of focal hyperplasia
Focal or nodular hyperplasia may or may not be able to…
concentrate iodine or synthesise TG
Initially, the hyperplasia is dependent upon…
TSH, but later the nodules become TSH-independent
Mutations of which gene have been found in a high proportion of nodules from patients with multinodular goitre?
gsp oncogene
Chronic activation of which protein results in thyroid cell proliferation and hyperfunction, even when TSH is suppressed?
the Gs protein
Patients with NTG usually present with?
thyroid enlargement, may be diffuse or multinodular
What indicates obstruction to jugular venous flow?
Positive Pemberton sign: facial flushing and dilation of cervical veins on lifting the arms over the head
The vast majority of patients with NTG are __.
euthyroid
Thyroid enlargement in NTG probably represents __ __.
compensated hypothyroidism
NTG treatment
- with the exception of those due to neoplasm, the current management of NTG consists simply of observation, without any specific therapy
- thyroid hormone suppression therapy rarely results in clinically significant decrements in goitre size
- T4 therapy may be required to suppress serum TSH levels (but could cause harm to elderly patients)