Thyroid Disorders Flashcards
1
Q
What is primary, secondary, tertiary hyperthyroidism?
A
- primary = thyroid problems
- secondary = pituitary problems but healthy thyroid. Overproduction of TH in response to a TSH-secreting tumour in anterior pituitary
- tertiary = hypothalamus problem
2
Q
What causes primary hyperthyroidism?
A
- Graves Disease (most common
- Toxic multinodular goitre
- Toxic adenoma
- Damage/inflammation of thyroid
- Iodine-induced thyrotoxicosis/Jod-Basedow syndrome
- Neonatal hyperthyroidism
- Drug induced hyperthyroidism (Iodine, Amiodarone, Lithium, Radiocontrast agents)
3
Q
Symptoms of hyperthyroidism (6), risks (for chronic) and complications associated
A
- Hyperphagia and Weight loss
- Heat intolerance
- Amenorrhoea, gynaecomastia (men) infertility, reduced libido
- Fatigue
- Tachycardia
- Goitre, Pretibial myxoedema, Ophthalmopathy in Graves
- Chronic = risk of congestive HF and osteoporosis
- Severe = thyroid storm
4
Q
How do you diagnose hyperthyroidism?
A
- TFT
- Low TSH, high T3, 4 = primary
- High TSH, high T3, 4 = pituitary tumour - Autoantibodies: TSHR-AB in graves
- Imaging: US or RAI + thyroid uptake scan
- if malignancy suspected or aetiology uncertain
5
Q
What is RAI uptake test? What does it show for: Graves disease, Thyroiditis, Nodule presence?
A
Once hyperthyroidism is confirmed, help determine the specific cause of the disorder.
- This is used to test for iodine in blood absorbed thyroid gland
- High uptake suggests Graves Disease
- Low uptake indicates hyperthyroidism is caused by inflammation/destruction of TG (thyroiditis)
- Uneven uptake indicates presence of nodule
- NOTE: pt eating high iodine foods (diary, seafood) will impact results
6
Q
Treatment and Management (5)
A
- Bb or CCB: treat adrenergic sx
- Thioamides/Anti-thyroid drug (ATD) e.g. carbimazole, methimazole, PTU
- Pregnancy = PTU for 1st, methimazole for 2nd, 3rd trimester
- ‘Block and Replace’ Regime: ATD + levothyroxine
- Titration Regime: ATD adjusted to achieve euthyroid - Radioiodine therapy
- Partially or completely destroy thyroid function, followed by replacement hormone therapy.
- 1st line for relapse graves - Surgery of thyroid
- if malignancy suspected, compressive goitre or RAI/ATD are unsuitable.
- complications: hypocalcaemia, recurrent laryngeal n. injury. - Steroids for Graves’ ophthalmopathy
7
Q
What is Grave’s disease? and it’s RF?
A
- Autoimmune disorder that affects the TG to cause HYPERthyroidism. Commonest cause of primary hyperthyroidism
- RF = women, aged 30-50yrs, Fx, Hx of autoimmune disorders
8
Q
Describe the pathophysiology of Graves and how it may cause ophthalmopathy
A
- B-cells produces thyroid-stimulating Ig that mimics TSH and binds to TG’s follicular cells as a result releases more T3 and T4
- This causes thyroid hypertrophy and hyperplasia
- Fibroblasts around the eyes and skin are also stimulated by antibodies and causes ophthalmopathy
9
Q
Investigations for Graves (5)
A
- TFT: High T3 and T4, low TSH
- Thyroid stimulating receptor autoantibodies (TSHR-AB)
- RAI uptake scan: uptake will be high and diffuse in GD
- Ultrasound of neck
- Biopsy/aspirate if goiter is suspicious of malignancy.
10
Q
What is primary hypothyroidism? And what causes it (6)?
A
- Iodine deficiency
- Common in low income countries - Hashimoto thyroiditis (most common)
- Amiodarone-induced hypothyroidism
- Postpartum thyroiditis (typically a transient change that occurs 6m after birth)
- Iatrogenic
- surgery or radioiodine therapy - Congenital defects
- Absence or abnormality of TG
11
Q
What is secondary hypothyroidism? And what causes it (5)?
A
- Tumour compressing hypothalamus or pituitary dec TRH or TSH production
- Radiation therapy to brain
- Sheehan syndrome
- Loss of blood during childbirth, resulting in severe low BP and body deprived of oxygen.
- Lack of oxygen causes damage to pituitary. - Central congenital hypothyroidism - TRH resistance
- Lymphocytic hypophysitis
- pituitary gland becomes infiltrated by lymphocytes, resulting in pituitary enlargement and impaired function
12
Q
Signs and Symptoms of hypothyroidism (6).
A
- Dec appetite & weight gain
- Cold intolerance
- Slowing of ANS: dec sweating, bradycardia, mental slowness, lethargy, constipation
- Myxoedema
- Puffy face, hands and feet
- High TSH levels stimulate fibroblasts in skin and soft tissues
- Fibroblasts start depositing ECM proteins in the interstitium - Galactorrhea, menorrhea
- elevated TRH causes elevated PL + TSH - Dry coarse skin, thinning hair
13
Q
What is Myxoedema Coma? Signs (4) + Mx?
A
- Rare but fatal outcome of hypothyroidism
- It is a medical emergency
- Usually occurs if hypothyroidism is poorly managed or individual undergoes stressful situation - serious infection or surgery.
- Sx of hypothyroidism becomes exaggerated
- Bradycardia
- Cognitive decline
- Hypotensive
- Hypothermic - Mx = IV levothyroxine, correct electrolyte imbalances and hypothermia
14
Q
Investigations for hypothyroidism (3)
A
- TFT
- Primary (hasimoto) = Raised TSH, Low T3, T4
- Secondary = Low/normal TSH, Low T3, T4 - TPOAbs
- anti-TPO or anti-thyroglobulin found in 90-95% of patients - Thyroid US U
- If pt has an asymmetrical goitre to rule out neoplastic lesions
- Assess thyroid size, if nodules are present
15
Q
Treatment and Management of hypothyroidism (3)
A
- Endocrinology referral for following:
- cardiac, endocrine conditions
- Goitre, nodule changes (2ww if malignancy suspected)
- After Tx adverse effects/not responding
- Female planning pregnancy
- Atypical TFTs - Levothyroxine (T4) monotherapy
- 1.6ug = <50yr no Hx of CVD
- 25ug = >50yrs, CVD, severe hypothyroidism
- Monitor TFT and adjust dose accordingly
16
Q
What is Hashimoto’s Thyroiditis?
A
- AI destruction of thyroid gland causing progressive fibrosis.
- Thyroid hormones dec -> hypothalamus + pituitary respond to this by inc TRH + TSH
- Inc in TSH, leads to thyroid enlargement
- Initially pts may show symptoms of hyperthyroidism - This compensation is short-lived and eventually the autoantibodies cause so much follicular cell damage that they destroy thyroid function altogether.
- When enough destruction occurs, pts exhibit symptoms of hypothyroidism
17
Q
Signs and symptoms of Hashimoto’s Thyroiditis (7).
A
- Weight gain
- Dry, coarse skin and hair
- Fatigue, exertional dyspnea, and exercise intolerance
- Due to limited pulmonary and cardiac reserve and increased muscle fatigue - Slowing ANS
- bradycardia, cold intolerance, dec sweating, memory loss, muscle cramps, joint pain, constipation - Heavy period and galactorrhoea
- Goitre related Sx
- voice hoarseness, difficulty swallowing - Myxoedema (severe cases)
18
Q
Treatment and Management of Hashimoto’s Thyroiditis
A
- PO Levothyroxine titrated
- Taken in the morning on an empty stomach for optimum absorption
- Not be given with iron, Ca supps, PPI to avoid suboptimal absorption
- <50years = 1.6ug/kg
- >50years, CVD = 25ug/day. Revaluated in 6-8w
- Pregnancy, short-bowel syndrome = Inc dose to maintain euthyroid state - Surgical Removal
- If goitre compressing on surrounding organs, suspected lymphoma
19
Q
Impact of thyroid disease on fetus and mother (untreated hypo and hyper [7,7] )
A
Untreated hypothyroidism
- Gestational hypertension and pre-eclampsia
- Placental abruption
- Post-partum haemorrhage
- Low birth weight
- Preterm delivery
- Neonatal goitre
- Neonatal respiratory distress
Untreated hyperthryoidism
- intrauterine growth restriction, IUGR
- Low birth weight
- Pre-eclampsia
- Preterm delivery
- Risk of stillbirth
- Risk of miscarriage
- Fetal malformation
20
Q
What drugs (5) can cause thyroid dysfunction
A
- Amiodarone
- Causes Hypo and hyper.
- HIGH iodine has a toxic effect on thyroid (Note: low levels of iodine is ok) - Lithium
- Interferone
- Immune therapies
- Dopamine decreases TSH secretion
21
Q
What is thyrotoxicosis?
A
- Medical condition caused by an excessive amount of thyroid hormones in the bloodstream
- Hyperthyroidism is the main cause
22
Q
Why may TFT differ in pregnancy? What is appropriately low in the 1st trimester?
A
- Thyroid function is altered in pregnancy due to INC METABOLIC REQUIREMENTS.
- HCG is released in 1st trimester and stimulates TSH-receptor, which leads to a fall in TSH in the 1st trimester.
- Low TSH levels would be seen and this is appropiate
23
Q
What is Transient gestational thyrotoxicosis
A
- hCG mediated hyperthyroidism
- Elevated hCG levels in 1st Trimester and stimulates TSH-R.
- Leading to an increase in T4 and T3 levels. Their levels peak by week 16 and remain high until delivery.
24
Q
Why may you give 250mcg of iodine during pregnancy?
A
- There is an increase in iodine requirement during pregnancy due:
- increase in maternal thyroid hormone production
- increase in renal iodine clearance,
- fetal iodine requirement - Dietary iodine requirements are higher during pregnancy
- Maternal iodine deficiency has adverse effects on the fetus including poor neurological and cognitive development
25
Both Graves and transient gestational thyrotoxicosis show dec TSH and inc T3, T4. How would you differentiate between these?
1. Low TSH levels in transient gestational thyrotoxicosis is due to hCG mediated stimulation of TSH-R.
2. Low TSH levels in Graves is due to Ig stimulation of TSH-R
3. Serology test - looking at TSH receptor antibodies elevated in blood test can be used to differentiate between the two conditions.
26
How would you treat hyper and hypothyroidism in pregnancy? And what is the goal of this treatment?
Hyper
- Low dose of antithyroid drug
- Goals is to maintain mild maternal hyperthyroidism while avoiding fetal hypothyroidism.
Hypo
- Thyroid hormone replacement
- Goal is to keep TSH level in trimester specific range
27
Treatment and Management of Graves during pregnancy (3).
1. ATD
- 1st trimester = PTU
- 2nd trimester = Methimazole used due to hepatotoxicity risk associated with PTU
2. Bblocker
- Short-term use for Sx control.
- Avoid long-term due to the risk of intrauterine fetal growth retardation
3. Thyroidectomy
- Only reserved for patients who cannot tolerate ATDs due to severe SE or when euthyroidism cannot be achieved
4. Radioactive iodine ablation is **CI** during pregnancy.
28
What is thyroid storm/thyrotoxic crisis? Signs (6), Mx?
- Medical emergency as a result of uncontrolled/untreated hyperthyroidism
- Signs = hyperthermia, tachycardia, arrhythmia, N+V, seizure, cognitive decline
- Mx: Bblockers, ATD, Steroids, Correct electrolyte imbalances, HF, hyperthemia, monitor BGL
- Dialysis and plasma exchange may be required
