hypothyroidism Flashcards
what is primary thyroid disease
disease affecting the thyroid gland itself
- can occur with or without goitre
- autoimmune usually
what is secondary hypothyroidism
- hypothalamic or pituitary disease
- no thyroid gland pathology
what thyroid hormones can be measured
- thyroid stimulating hormone (TSH)
- free T4
- free T3
what is the pathway of organs of the hypothalamic pituitary thyroid axis
hypothalamus > pituitary > thyroid > liver
hormone levels in primary hypothyroidism
- free T3/4 low
- TSH high
hormone levels in primary hyperthyroidism
- free T3/4 high
- TSH low
hormone levels in secondary hypothyroidism
- free T3/4 low
- TSH low or normal
hormone levels in secondary hyperthyroidism
- free T3/4 high
- TSH high or normal
what is hypothyroidism
results from any disorder that results in insufficient secretion of thyroid hormones from the thyroid gland
what is myxoedema
severe hypothyroidism and is a medical emergency
what is pretibial myxoedema
rare clinical sign of Grave’s disease
goitrous causes of hypothyroidism
- hashimoto’s
- iodine deficiency
- drug-induced
- maternally transmitted
- hereditary biosynthetic defects
non-goitrous causes of hypothyroidism
- atrophic thyroiditis
- post ablative therapy
- post radiotherapy
- congenital defects
self-limiting causes of hypothyroidism
- withdrawal of antithyroid drugs
- subacute thyroiditis
- post-partum thyroiditis
secondary hypothyroidism causes
-infiltrative
-infectious
-malignant
-traumatic
-congenital
etc
what is the most common cause of hypothyroidism
hashimoto’s
what is hashimoto’s
autoimmune destruction of thyroid gland and reduced thyroid hormone destruction
what is hashimoto’s characterised by
- antibodies against thyroid peroxidase
- T-cell infiltrate and inflammation microorganisms
clinical features of hypothyroidism
- coarse, sparse hair
- dull, expressionless face
- periorbital puffiness
- pale cool skin
- vitiligo
- hypercarotenaemia
- cold intolerance
- pitting oedema
- hyperlipidaemia
- decrease appetite
- weight gain
cardiac features of hypothyroidism
- reduced HR
- cardiac dilatation
- pericardial effusion
- worsening of heart failure
GI features of hypothyroidism
- constipation
- megacolon and intestinal obstruction
- ascites
resp features of hypothyoridism
- deep hoarse voice
- macroglossia
- obstructive sleep apnoea
neurological features of hypothyroidism
- decreased intellectual and motor activities
- depression, psychosis
- muscle stiffness, cramps
- peripheral neuropathy
- prolongation of tendon jerks
- carpal tunnel syndrome
- decreased visual acuity
gynae features of hypothyroidism
- menorrhagia
- later oligo- or amenorrhea
- hyperprolactinaemia
antibodies present in hypothyroidism
- anti TPO
- anti thyroglobulin
- TSH receptor antibody
management of hypothyroidism
YOUNG
-start levothyroxine at 50-100 ug daily
OLD
-start levothyroxine at 25-50 ug daily, adjust every 4 weeks
check TSH 2 months after any dose change
once stabilised TSH should be checked every 12-18 months
management for secondary hypothyroidism
titrate dose of levothyroxine to fT4 levels
should thyroxine be taken after food?
no should be taken on an empty stomach
what should be done to the dose of levothyroxine in pregnancy
increased by 25-50%
who gets myxoedema coma
elderly women with long standing but frequently unrecognised or untreated hypothyroidism
ECG findings of myxoedema coma
- bradycardia
- low voltage complexes
- varying degrees of heart block
- T wave inversion
- prolongation of QT interval
resp findings of myxoedema coma
type 2 respiratory failure
how do you treat myxoedema coma
- ABC
- rewarm
- cardiac monitoring
- monitor urine output
- broad spectrum antibiotics
- thyroxine cautiously
what is thyrotoxicosis
clinical, physiological and biochemical state arising when the tissues are exposed to excess thyroid hormone
what is hyperthyroidism
conditions in which overactivity of the thyroid leads to thyrotoxicosis
cardiac symptoms of hyperthyroidism
- palpitation , AF
- cardiac failure
sympathetic symptoms of hyperthyroidism
- tremor
- sweating
CNS hyperthyroidism symptoms
- anxiety
- nervousness
- irritability
- sleep disturbances
other symptoms of hyperthyroidism (GI, vision, hair, skin)
- frequent loose bowel movements
- lid retraction
- double vision
- proptosis
- brittle thin hair
- rapid fingernail growth
reproductive symptoms of hyperthyroidism
- menstrual cycle changes
- lighter bleeding and less frequent periods
msk symptoms of hyperthyroidism
muscle weakness
-especially in thighs and upper arms
metabolism symptoms of hyperthyroidism
weight loss despite increased appetite
thermogenesis symptom of hyperthyroidism
intolerance to heat
causes of hyperthyroidism
- Graves disease
- hashitoxicosis
- thyrotropinoma
- thyroid cancer
- choriocarcinoma
- thyroid nodules with autonomous function
- thyroid inflammation
- over treatment with levothyroxine
- thyrotoxicosis factitia
- metastatic thyroid carcinoma
lab findings of Grave’s disease
- decreased TSH
- increase free T4/3
clinical signs specific to Grave’s disease
- pretibial myxoedema
- thyroid acropachy
- thyroid bruit
- Grave’s eye disease
how is mild grave’s eye disease treated
topically with lubricants
how is severe grave’s eye disease treated
- steroids
- radiotherapy
- surgery
who gets nodular thyroid disease
older patients
tests for nodular thyroid disease
- increase fT4/3
- decrease TSH
- high uptake of scintigraphy
- thyroid US
- antibody NEGATIVE (TRAb)
what happens in thyroid storm
- severe hyperthyroidism
- resp and cardiac collapse
- hyperthermia
- exaggerated reflexes
- typically seen in hyperthyroid patients with an acute infection/illness
treatment for thyroid storm
- Lugol’s iodine
- glucocorticoids
- PTU
- beta blockers
- fluids
- monitoring
treatment for hyperthyroidism
carbimazole
-1st line, once daily
Beta blockers
-propanolol
prophylthiouracil
-1st line only in 1st trimester of pregnancy, twice daily
Radioiodine
- 1st choice for relapse of Grave’s disease and nodular thyroid disease
- contraindicated in pregnancy
side effect of Carbimazole
risk of aplasia cutis in early pregnancy
Grave’s disease treatment
Carbimazole for 4-8 weeksOnce the patient has normal thyroid hormone levels, they continue on maintenance carbimazole and either:
- The dose is carefully titrated to maintain normal levels (known as “titration-block”)
- The dose is sufficient to block all production and the patient takes levothyroxine titrated to effect (known as “block and replace”)
side effects of ATDs
- cholestatic jaundice
- rash, urticaria
- fulminant hepatic failure
- agranulocytosis (life threatening blood disorder)
causes of thyroiditis
- Hashimoto’s
- De Quervain’s
- post partum
- drug induced
- radiation
- acute suppurative thyroiditis
subacute thyroiditis trigger and symptoms
- triggered by viral infection
- neck tenderness
- fever
- other viral symptoms
what is subclinical thyroid disease
abnormal TSH with normal thyroid hormone levels
when is treatment advised in subclinical hypothyroidism
when TSH is >10
when is treatment advised in subclinical hyperthyroidism
if TSH < 0.1
what are non-thyroidal issues
refers to the impact of intercurrent illness (e.g. infection) on the HPT axis
-TSH typically suppressed initially then rises during recovery
