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Gaby’s Green Top Guidelines > 2025 76 Thyroid Disorders > Flashcards

2025 76 Thyroid Disorders Flashcards

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1
Q

What are the reference ranges for TSH & fT4 in pregnancy?

A

Trimester & manufacturer-specific!
Or TSH upper limit 4

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2
Q

What is the recommended daily intake of iodine surrounding pregnancy? How can it be obtained?

A

200-250 micrograms
Dietary increase
Supplement 150 as KI

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3
Q

When should subpopulations with specific risk factors for thyroid disease be tested?

A

1st trimester

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4
Q

Pre-pregnancy, how should SCH be managed?

A
  1. Severe (TSH > 10), levothyroxine until TSH ≤ 2.5
  2. General (upper normal to 10), esp TPO +ve, consider levo
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5
Q

During pregnancy, how should SCH be managed?

A

Consider levo, esp if diagnosed 1st trimester

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6
Q

How should hypothyroidism be managed pre- & during pregnancy?

A
  1. Titrate levo until TSH ≤ 2.5
  2. Self-initiate 25-30% increase following +ve UPT
  3. Test every 4-6w until 20/40, then once at 28/40
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7
Q

What are the recommendations around TPO Ab?

A
  1. Do not test routinely if euthyroid
  2. If +ve & euthyroid, don’t treat, but test in 1st trimester & at 20/40
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8
Q

What are the recommendations for hyperthyroidism?

A
  1. Switch CMZ to PTU pre-pregnancy
  2. If conceive on CMZ, switch to PTU before 10/40
  3. Lowest effective dose to keep fT4 in upper half ref range
  4. If euthyroid for 6+m on low dose, consider discontinuing & monitoring
  5. Monitor every 2-4/40, consider 4-8/40 after 20/40
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9
Q

What are the differentials for new finding of TSH suppression & fT4 rise in pregnancy?

A

Graves’ disease
Toxic nodular hyperthyroidism
Gestational transient thyrotoxicosis

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10
Q

What is the Mx of gestational transient thyrotoxicosis & subclinical hyperthyroidism?

A

Symptomatic & supportive only

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11
Q

How much does the demand for maternal thyroid hormones increase in pregnancy?

A

50%

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12
Q

How do thyroid-related hormones change in pregnancy?

A
  1. hCG transiently raises fT4 & fT3
  2. Oestrogen raises TBG up to plateau 20/40
  3. T3 & T4 production increases to 20/40
  4. From 20/40, T3 & T4 decline gradually & TSH rises slightly
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13
Q

How does the fetus manage thyroid hormones?

A
  1. Placenta stores iodine
  2. Fetus takes up iodine from 10-12/40
  3. Fetus produces T3 & T4 from 18-22/40
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14
Q

When in pregnancy are thyroid hormones particularly important & why?

A

1st 20/40
For neurodevelopment

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15
Q

What is the leading cause worldwide of preventable neurodevelopmental disease?

A

Iodine deficiency

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16
Q

What are the risks in severe iodine deficiency?

A
  1. Endemic goitre
  2. Hypothyroidism
  3. Neurological, developmental & intellectual impairment
  4. Subfertility
  5. Miscarriage
  6. Infant mortality
  7. Trophoblastic or embryonic disorders
  8. Deaf-mutism
  9. Motor rigidity
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17
Q

What is the most common aetiology of thyroid disorders in iodine-replete areas?

A

Autoimmunity

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18
Q

What risks are associated with inadequately treated overt hypothyroidism?

A
  1. Miscarriage
  2. Perinatal death
  3. PIH & PET
  4. Preterm birth
  5. Low birth weight
  6. PPH
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19
Q

What risks are associated with overt hyperthyroidism?

A
  1. PET
  2. Preterm birth
  3. FGR
  4. Maternal heart failure
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20
Q

What is the pathophysiology in Graves disease?

A

TSH receptor antibodies, stimulating

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21
Q

Antithyroid antibodies: what is the most common & the overall prevalence?

A

Anti-TPO
5-31%
10% of miscarriage/subfertlity

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22
Q

What is the prevalence of thyroid disease in pregnancy?

A

Overt hypo: 0.2-1%
SCH: 2.2-10%
Isolated H: 1.3-8%
Overt hyper: 0.05-1.3%
Sub hyper: 1.5-2%
GTT: 1-5%

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23
Q

What are the symptoms of acute iodine poisoning?

Study These Flashcards
A

Gastrointestinal
Cardiovascular
Coma

24
Q

What is the maximum daily iodine intake?

Study These Flashcards
A

500 micrograms

25
In what proportion of patients is hypothyroidism asymptomatic?
70%
26
In which groups of women should targeted thyroid function testing be triggered?
1. Personal hx of thyroid condition or previous insult 2. Autoimmune conditions associated with obstetric complication 3. Previous late pregnancy loss
27
Which non-thyroid insults should trigger thyroid testing?
1. Cardiac dysthymia 2. Significant preconception weight loss 3. Medications: amiodarone, lithium 4. Previous head/neck irradiation
28
Which autoimmune conditions trigger thyroid testing?
1. T1DM 2. SLE 3. Anti-Ro/anti-La +ve 4. Antiphospholipid syndrome
29
What is the annual rate of progression of SCH to OH in non-pregnant population?
2-6%
30
How should self-initiated levothyroxine dose be increased?
1. By 25-30% 2. Either double dose 2 days a week 3. Or increase by 25mcg a day if on ≤ 100mcg a day 4. Or 50mcg a day if on ≥ 100mcg a day
31
What dose of thyroxine should people be started on, and how is this reviewed?
1. 1.6mcg/kg for OH & severe SCH 2. 1-1.2mcg/kg for general SCH 3. Review 4 weeks later
32
What proportion of women need a further thyroid dose adjustment after empirical increase?
40%
33
What is an alternative to levothyroxine if unable to tolerate due to NVP?
IV liothyronine, under discussion with endocrinologist
34
When should repeat TFTs be taken postnatally?
6-8 weeks
35
What is the definitive Tx for Graves’ disease & how does it impact on pregnancy?
1. Radioactive iodine, or thyroidectomy 2. Wait 6 months before TTC, and longer if post-Tx Abs remain high
36
What is the dose ratio when changing carbimazole to propylthiouracil?
1:20
37
Which thyroid conditions should be monitored with serial growth scans from 26-28/40?
1. Graves’ disease 2. Hyperthyroid requiring Tx 3. Detectable TRAb
38
What are the risks of thionamides?
Minor eg rash 3-5% Agranulocytosis 0.15% Liver failure 0.1% (PTU)
39
What are the teratogenic effects of carbimazole?
1. Dysmorphic features 2. Aplasia cutis 3. Choanal & oesophageal atresia 4. Abdominal wall defects 5. Urinary abnormalities 6. Eye abnormalities 7. Ventricular septal defects
40
What is the period of highest teratogenic risk with carbimazole?
6-10 weeks
41
How is antithyroid medication adjusted in pregnancy?
1. Discontinue if euthyroid > 6m 2. Many reduce dose as pregnancy progresses & can stop in 2nd or 3rd trimester 3. If still need Tx beyond 20/40, consider switch back to CMZ to avoid hepatotoxicity
42
Which TFT is important for a) hypothyroid, b) hyperthyroid monitoring?
a) TSH b) Free T4
43
In what cases & when should thyroidectomy be considered in pregnancy?
1. Severe maternal adverse effects to antithyroid drugs 2. Large goitre compromising airway 3. 16-22/40
44
In what proportion of women with Graves’ disease does fetal & neonatal hyperthyroidism occur?
1-5%
45
What clinical features suggest Graves’ disease over gestational transient thyrotoxicosis?
1. Sx before pregnancy 2. Less likely to have HG 3. Personal or FHx thyroid 50% 4. Diffuse goitre 90% 5. Thyroid eye disease 20% 6. fT3 & TRAb raised
46
What is the pathophysiology of gestational transient thyrotoxicosis?
hCG stimulation of TSH receptors Worse in multiple pregnancy & GTD
47
What is the prevalence of thyroid nodules in pregnancy?
1% in non-iodine-deficient areas 15-21% in mild to moderate iodine deficiency
48
What is the prevalence of thyroid cancer in pregnancy?
14:100,000
49
What is the Mx of thyroid nodules in pregnancy?
1. Check TFTs 2. Specialist referral 3. Fine needle aspiration at any stage of pregnancy if Ca suspect 4. If surgery needed, for airway compression, 14-22/40 5. Obs anaesthetic review
50
What is the effect of pregnancy on the risk of thyroid cancer progression & recurrence?
1. No change in rate of recurrence or long-term survival 2. Generally surgery can be deferred, unless substantial growth, airway compression or rapidly progressive disease
51
What is postpartum thyroiditis?
Thyroid dysfunction With no other thyroid disease Within 12 months postpartum Due to TPO & thyroglobulin Abs Due to reactivation of immune system after preg suppression
52
What is the time course of postpartum thyroiditis?
1. Thyrotoxicosis, 2-6m to 12m 2. Transient hypothyroid, 3-12m, to permanent in 50% 3. Euthyroid
53
How should postpartum thyroiditis be managed?
1. No antithyroid drugs 2. Symptomatic beta blockers 3. Levothyroxine if symptomatic 4. Monitoring every 6 weeks 5. Annual TSH once resolved 6. Test when planning pregnancy
54
How can postpartum thyroiditis be diagnosed?
1. Test women with risk factors 2. Serial TFTs every 6 weeks 3. If thyrotoxicosis, test TRAb & consider isotope scan (uptake in Graves but not PPT) 4. US: Non-homogenous hypoechogenic texture 5. Histopath: lymphocytic infiltration
55
What are the outer limits of TSH & T4 for all manufacturers & trimesters?
TSH: 0.06-4 fT4: 6-20

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