2.3 Disorders of Thyroid Hormone Excess and Deficiency Flashcards
As an example, explain the levels of TSH/T3 & T4 that you’d expect to see in primary hypothyroidism
- 1° means failure is at level of thyroid
- Therefore, TSH levels would still be high, since the body is trying to make T3 and T4
- However, since the thyroid cannot do this, our T3 & T4 levels are decreased
The levels of which two hormones in Thyroid Function Tests tell us whether a patient has hypo/hyperthyroidism?
Levels of T3 and T4. High = hyper, low = hypo.
Which is more potent: free T4 or free T3?
Free T3.
Where in the cell are the receptors for thyroid hormones? What does this tell us about the properties of thyroid hormones?
Within the nucleus. Hence, we remember that thyroid hormones are lipophilic, and are carried through the blood on carrier proteins to prevent precipitating out.
There are two main ways in which hyperthyroidism can cause increased thyroid hormone. What are these?
- Increased production of thyroid hormones
- Increased release due to breakdown of tissue, such as in thyroiditis
List some different types of hyperthyroidism
- Grave’s disease (TSI release)
- Toxic nodular goitre
- Toxic multinodular goitre
- Thyroiditis
- Thyrotoxicosis from exogenous source
- HCG mediated
- Secondary (increased TSH production)
What is thyroid storm? What are its symptoms?
- Extreme overproduction of thyroid hormone
- Symptoms include hyperpyrexia, cardiovascular compromise, altered conscious state, and other symptoms of hyperthyroidism (agitation, heat intolerance, tremor, tachycardia etc.)
What hyperthyroidism symptoms are specifically associated with Grave’s disease?
- Smooth goitre
- Pretibial myxedema
- Thyroid eye disease (exophthalmos, grittiness/dryness of eyes)
What are some specific PMHx and FHx signs of Grave’s disease
PMHx: other autoimmune thyroid conditions (e.g. Hashimoto’s), and other autoimmune conditions
FHx: Affected family members
What’s the difference between Grave’s disease and toxic nodular/multinodular goitre? How does the pathophys differ?
- In TMG, a mutation in TSH Receptor allows autonomous activation of nodules of the thyroid
- Unlike grave’s where the whole thyroid is affected by TSI, this can be in one or more Goitre
What is the most common cause of thyroiditis? What is thought to cause this?
- Most common is subacute thyroiditis
- Thought to occur in a post-viral setting
List five common causes of hypothyroidism
- Hashimoto’s
- Thyroidectomy
- Iodine deficiency
- Secondary/central hypothyroidism
- Radiation exposure
What immune cells are involved in the pathogenesis of Hashimoto’s Thyroiditis? How are T3 and T4 levels affected over time?
- T-Cell Mediated, autoimmune invasion of the thyroid
- Can cause increase initially as preformed T3 and T4 are released, then decrease
How is it thought that hyperthyroidism increases risk of Atrial Fibrillation/tachycardia? Why is this important in terms of cardiovascular risk?
- Increase in sympathetic tone (increased density of beta receptors in cardiac myocytes)
- Over time, can lead to atrial remodelling, disturbing electrical flow and causing arrhythmias such as AF, and generalised increase in HR
- This is important because it can increase risk of thromboembolic events, as AF does
What can cause cause neonatal hypothyroidism? What are the possible effects of this, and what do we do as a result?
- Can be caused by issues with synthesis, or resistance to thyroid hormones
- If untreated, can lead to developmental delay, intellectual disability, and less growth
- Therefore, we routinely screen for neonatal hypothyroidism
