ENDO - Thyroid disease Flashcards Preview

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Flashcards in ENDO - Thyroid disease Deck (19):
1

describe the common conditions that can lead to hyper and hypo functioning of the thyroid gland

Hyperthyroidism:
- Autoimmune (Grave's disease)
- toxic nodular goitre (multinodular or solitary adenoma)
- iodine-induced (radiographic contrast, amiodarone)
- Iatrogenic (too much thyroxine use)
- Transient (thyroiditis)

Hypothyroidism:
- Autoimmune (Hashimoto's thyroiditis, atrophic thyroiditis)
- Iatrogenic: 131I treatment, thyroidectomy, irradiation
- drugs: iodine excess (lithium, antithyroid drugs)
- iodine deficiency (prevalent in poor countries)

2

list the clinical features of hyperthyroidism and hypothyroidism

Hyperthyroidism:
•Heat intolerance
•Loss of weight
•Increase in appetite
•Increase in sweating
•Tremulousness
•Anxiety, emotional lability
•Loss of hair
•Increased frequency of bowel movements
•Menstrual irregularity
*in elderly pt, hyperthyroidism may have few symptoms/signs

Hypothyroidism:
•Malaise, tiredness, myalgia, depression
•Cold intolerance, constipation, weight gain
•Delayed tendon reflexes, bradycardia, myxoedema, voice change, myopathy, hypothermia, effusions

3

What are the thyroid function tests and what do they mean?

Check TRH, HSH, free T4

If low T4, high TSH: primary (no negative feedback)

If low T4, low TSH: secondary (pituitary itself is not working)

4

list the appropriate radiological or nuclear medicine imaging tests to diagnose common thyroid disorders

Thyroid nuclear scan: Tc-99m Pertechnetate commonly used
- Normal: thyroid uptake similar to salivary gland uptake
- Grave's disease: Homogenous increased uptake (compare with salivary gland)
- Toxic-nodular disease: localised increased uptake with suppression of uptake in the rest
- Multinodular goitre: heterogenous increased uptake

5

describe the different therapeutic agents used to treat thyroid disease (hyper & hypo)

Hyperthyroidism:
- antithyroid drugs; carbimazole, propylthiouracil
- radioactive iodine (to kill some thyroid cells)
- surgery; if adverse reactions to drugs, cosmetic preference, risk of malignancy

Hypothyroidism:
• Usually thyroxine 75 -150 mcg/day, single dose
•Some patients – 50 or even 25 mcg/day as a starting dose
•Aim for TSH in the low normal range (rather than T4)

6

explain how to monitor the thyroid status of a patient once treated

- regular check of TFT after 6 weeks of change of medications

7

How do you diagnose hypothyroidism?

•Check TSH
•Reconfirm elevated TSH, confirm FT4 is low – (some weeks apart?)
•Correlate with symptoms and clinical examination
•Consider a thyroid ultrasound only if there is a palpable goitre
•NO NEED for a nuclear scan (c.f. Hyperthyroidism)
•Anti-thyroid antibodies (anti-thyroid peroxidase - TPO) can sometimes be helpful in this situation – especially if the TSH is borderline elevated

8

Rx of hypothyroidism

• Usually thyroxine 75 -150 mcg/day, single dose
•Some patients – 50 or even 25 mcg/day as a starting dose
•Aim for TSH in the low normal range (rather than T4)

9

What are the common mistakes made in treating hypothyroidism?

•Only adjust thyroxine dose after 6-8 weeks
•Do not order a nuclear scan test in hypothyroidism
•There is no hurry except in pregnancy
•To be taken separately from medications that may decrease thyroxine absorption
–Iron tablets
–Calcium tablets
–Antacids
–Cholestyramine

10

DDx of feeling tired, palpitations, panic, SOB at times, insomnia for 2 months

–Caffeine or cola drinks in excess (COMMON!)
–Thyrotoxicosis
–Anxiety or panic disorder
–A primary pulmonary or cardiac disorder

11

What should you not forget to ask in a suspected hyperthyroid Hx?

- Intake of caffeine/cola/energy drinks
- use of medications (e.g. amiodarone or any weight-loss inducin drugs etc)

12

What should you look for in hyperthyroid exam?

–Heart rate and rhythm (any AF?). ECG?
–TREMOR
–Skin, nail and hair changes (often normal)
–Thyroid size, consistency, bruit
•May have a diffuse soft goitre
•May have a bruit over the thyroid
–Usually no cervical lymph nodes

13

Ix of hyperthyroidism. What do you expect to see?

•TSH is very low – less than 0.1
•FT4 and/or FT3 are elevated
•Re-confirm the result
•Consider a nuclear scan
–Not in pregnancy
–Distinguishes between Graves’ disease, toxic nodular disease, iodine or thyroiditis-induced thyrotoxicosis and factitious
•Antibodies against the TSH receptor are often present in high titres and may help confirm the cause of thyrotoxicosis and provide some prognostic information

14

Rx of hyperthyroidism

- antithyroid drugs; carbimazole, propylthiouracil. May be curative (need short term) in Grave's disease but not in toxic nodular disease (need permanently).
- radioactive iodine (to kill some thyroid cells)
- surgery; if adverse reactions to drugs, cosmetic preference, risk of malignancy

15

Name 2 anti-thyroid drugs used to treat hyperthyroidism

carbimazole, propylthiouracil

16

Describe Rx of Grave's disease & toxic nodular disease with antithyroid drugs

Graves’ disease:
–Need to treat for 12-18 months
–Usually 10 to 40 mg (higher dose than toxic nodular disease) carbimazole a day in divided doses)
–Adjust dose ever 6 weeks or so (gradual reduction in doses depending on clinical state and TFTs)
–Initially b-blockers (to help with cardiac symptoms) may help alleviate symptoms

Toxic nodular disease:
–Likely to need long term treatment
–Low doses are usually effective (5-10 mg CBZ a day)

17

Describe radioactive iodine as Rx for hyperthyroidism

•Very effective, permanent
•(-): Permanent hypothyroidism frequent outcome
•Small risk of thyroid eye disease
•Patient must not be pregnant
•Must not have had ordinary iodine for months (radiographic contrast, kelp etc)

18

What are common mistakes made in Ix of hyperthyroidism?

•Requesting an ultrasound in hyperthyroidism
•Even worse is performing a contrast CT scan
•Asking for antithyroid antibodies (anti-TSH receptor antibodies can be helpful)
•Checking TFTs and adjusting treatment outside the 4 to 12 week interval

19

Describe subclinical hypothyroidism

•TSH elevated but FT4 and FT3 NORMAL
•Increased (but still small) risk of overt hypothyroidism
•Possible increased cardiovascular risk in long-term (evidence is not conclusive)
•Observe or treat according to clinical circumstances
•Anti-TPO antibodies may be helpful as high titres increase the risk of progression to overt hypothyroidism

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