Thyroid Disorders Flashcards
What can go wrong with the thyroid?
Decreased function - hypo Increased function - hyper Enlargement - nodular disease Inflammation (AutoAb) Cancer
Most common causes of hypothyroidism?
a. Iodine deficiency (most common worldwide)
In Aus:
b. Autoimmune chronic lymphocytic thyroiditis (Hashimoto thyroiditis, atrophic thyroiditis)
c. Congenital: error in synthesis of thyroxine
d. Rx: surgery for hyper in the past
e. Transient: silent thyroiditis including postpartum thyroiditis (rebound hypothyroid phase when thyroid is damaged after inflammation e.g. virus)
Ix of hypothyroidism?
TSH: elevated
Free T3: low
Free T4: low
Thyroid Ab (anti-TPO, anti- thyroglobulin)
- Imaging is not indicated in hypothyroidism
- Consider a thyroid US only if there is a palpable goitre
- No need for nuclear scan
Sx of hypothyroidism - appearance
Puffy, pale facies Dry, brittle hair Dry, cool skin Thickened brittle nails Myxoedema
Sx of hypothyroidism - energy
Cold intolerance
Weight gain
Fatigue
Sx of hypothyroidism - nervous system
Headache
Sx of hypothyroidism - cognitive
d
Sx of hypothyroidism - Cardiovascular
d
Sx of hypothyroidism -
d
Sx of hypothyroidism -
d
Sx of hypothyroidism -
d
What is the difference between primary and secondary hypothyroidism?
Primary hypothyroidism - pathology of thyroid itself
(raised TSH, low free T3/T4)
Secondary hypothyroidism - pathology of higher centre (anterior pituitary - low TSH, low free T3, T4)
Rx of hypothyroidism
Thyroxine - 75-150mcg/day single dose (if young, healthy, pregnant)
Aim for TSH in low normal range
If patient has IHD or elderly, start with smaller dose at 25 mcg/day
Rx of hypothyroidism
What is the 1/2 life of treatment and how does that affect follow up?
What are the modifying factors of Rx?
Thyroxine - 75-150mcg/day single dose (if young, healthy, pregnant)
Half life: 1 week therefore steady state app. 6-8 weeks, only do blood test and adjust thyroxine dose after 6-8 weeks
Aim for TSH in low normal range
Modifying factors:
If patient has IHD or elderly, start with smaller dose at 25 mcg/day
What medications decrease thyroxine absorption?
Fe tablets, Ca tablets, antacids, cholestyramine
There is usually no hurry in hypothyrodism Rx except in…?
Pregnancy
Ix of hypothyroidism?
TSH: elevated
Free T3: low
Free T4: low
Thyroid Ab (anti-TPO, anti- thyroglobulin)
- Recheck TFTs after 6 weeks (except in pregnancy)
- Imaging is not indicated in hypothyroidism
- Consider a thyroid US only if there is a palpable goitre
- No need for nuclear scan
There is usually no hurry in hypothyrodism Rx except in…?
Pregnancy
T/F recheck TFTs later than 6 weeks
True - no point checking earlier
T/F adjust Rx earlier than 6 weeks
False - half life of thyroxine is 1 week therefore steady state is reached at 6-8 weeks (no point checking before)
T/F it is appropriate to request a nuclear scan in hypothyroidism
False
Sx of hypothyroidism - cognitive
Depression
Delayed tendon reflexes
Sx of hypothyroidism - Cardiovascular
Bradycardia
Pericardial effusion
Decreased exercise tolerance
Sx of hypothyroidism - GIT
Constipation
Anorexia
Sx of hypothyroidism - reproductive
irregular and heavy menses
Infertility
T/F it is appropriate to request a nuclear scan in hypothyroidism
False
Relationship between pregnancy and hypothyroidism
Iodine supplementation should be prescribed routinely in women planning a pregnancy
Maternal TFTs change during pregnancy in response to increased metabolic requirements and presence of fetus
Therefore require trimester specific reference intervals
Relationship between pregnancy and hypothyroidism
Iodine supplementation should be prescribed routinely in women planning a pregnancy
Maternal TFTs change during pregnancy in response to increased metabolic requirements and presence of fetus (esp. thyrotropic activity of B-hCG results in decrease in TSH in first trimester)
Therefore require trimester specific reference intervals
Relationship between pregnancy and hypothyroidism
Iodine supplementation should be prescribed routinely in women planning a pregnancy
Maternal TFTs change during pregnancy in response to increased metabolic requirements and presence of fetus (esp. thyrotropic activity of B-hCG results in decrease in TSH in first trimester)
Therefore require trimester specific reference intervals
Relationship between pregnancy and hypothyroidism
Iodine supplementation should be prescribed routinely in women planning a pregnancy
Maternal TFTs change during pregnancy in response to increased metabolic requirements and presence of fetus (esp. thyrotropic activity of B-hCG results in decrease in TSH in first trimester)
Therefore require trimester specific reference intervals
Causes of thyrotoxicosis
a. Graves’ disease
b. Toxic nodular goitre (multinodular, solitary adenoma)
c. Iodine - induced
- radiographic contrast
- naturapathic remedies
- amiodarone
d. Factitious (surreptitious thyroxine use) - for weight loss
e. Transient (with thyroiditis)
Ix hyperthyroidism
a. TSH: Low (usually
Sx of hyperthyroidism
Heat intolerance Loss of weight Increase appetite Increase in sweating Tremor Anxiety, emotional lability Loss of hair increased f of bowel movements Menstrual irregularity
Signs of hyperthyroidism on Px ** finish with Talley xx
Increase HR and rhythm Tremore Skin, nail and hair changes Thyroid size, consistency, bruit Usually no cervical LNs Eyes: redness, irritation (conjunctival), exopthalmos, proptosis, lid lag, double vision
In a thyroid nuclear scan, what should the thyroid uptake be compared to?
in a normal thyroid nuclear scan, thryoid uptake is similar to salivary gland uptake
In a thyroid nuclear scan, what should the thyroid uptake be compared to?
in a normal thyroid nuclear scan, thryoid uptake is similar to salivary gland uptake
Rx of hyperthyroidism
- Antithyroid drugs:
a. Carbimazole
b. Propylthiouracil (PTU) - Radioactive iodine
- Surgery: only if other reasons such as - AFx to Rx, cosmetic, risk of malignancy
When do you use carbimazole?
used in most cases:
- more effective
except in first trimester: teratogenic
When do you use PTU?
1st trimester of pregnancy as carbimazole associated with teratogenic effects
Not used as much:
Liver failure
When do you use PTU?
1st trimester of pregnancy as carbimazole associated with teratogenic effects
Not used as much:
Liver failure
AFx of carbimazole and PTU?
Carbimazole: rash, prirutis (agranulocytosis - rare)
PTU: agranulocytosis, liver damage
When do you use carbimazole?
- used in most cases
- more effective
except in first trimester: teratogenic
Rx of hyperthyroidism
- Antithyroid drugs:
a. Carbimazole (CBZ)
b. Propylthiouracil (PTU) - Radioactive iodine
- Surgery: only if other reasons such as - AFx to Rx, cosmetic, risk of malignancy
AFx of carbimazole and PTU?
Carbimazole: rash, prirutis (agranulocytosis - rare)
PTU: agranulocytosis, liver damage
Outline in detail the Rx of Graves’ disease
- Need to treat 12-18 months
- 10-40mg carbimazole a day
- Adjust dose over 6 weeks (gradual reduction in doses depending on clinical state)
Outline Rx of toxic nodular disease
Long term Rx of low doses 5-10mg CBZ/day
What is are the contraindications of radioactive iodine Rx?
- Pregnancy
2.Eye disease in Graves’
(two factors worsen exopthalmos - smoking and radioactive iodine)
What is are the contraindications of radioactive iodine Rx?
- Pregnancy
2.Eye disease in Graves’
(two factors worsen exopthalmos - smoking and radioactive iodine)
T/F ask for anti-thyroid Ab if suspecting Graves’
F - anti TSH receptor Ab
T/F check TFTs and adjust Rx within the 4-12 week interval
T - steady state of Rx is between 4-12 weeks
What is subclinical hypothyroidism?
d