Hypothyroidism Flashcards
outline the typical presentation of hypothyroidism?
Hashimotos: cold intolerance, weight gain, C, dry skin, hair loss, hoarseness, mental slowness, depression, irreg cycles, firm diffuse goitre - anti-TPO, anti-tG, AMA - can cause non-megaloblastic anaemia - associated with Non-hodgkin’s lymphoma MAY BE EASILY CONFUSED AS ALZHEIMER’S Myxoedema coma: hypoventilating, hypothermia, hyponatremia, confusion, coma, HF
define hypothyroidism?
Clinical syndrome resulting from insufficiency of thyroid hormones
what are the risk factors for hypothyroidism?
iodine deficiency
female sex
middle age
family history of autoimmune thyroiditis
what are the causes of acquired primary hypothyroidism?
PRIMARY= DECREASED THYROID HORMONE PRODUCTION
Hashimoto’s thyroiditis (autoimmune)
Iatrogenic (post-surgery, radioiodine, hyperthyroid medication, amiodarone or lithium)
Severe iodine deficiency – poor diet in “developing” countries
Iodine excess (Wolff-Chaikoff effect)
Thyroiditis
what are the causes of congenital primary hypothyroidism?
Thyroid dysgenesis
Inherited defects in thyroid hormone biosynthesis
what are the causes of secondary hypothryoidism?
Pituitary and Hypothalamic Disease - resulting in reduced TSH and TRH and, hence, reduced stimulation of thyroid hormone production
‘Subclinical’ hypothyroidism describes a normal serum T4 with an elevated serum TSH.
Primary myxoedema ( spontaneous atrophic hypothyroidism): idiopathic reduction in the production of thyroid hormones with no goitre
Sick euthyroid syndrome is the presence of low TSH, T3 and/or T4 but with a normal functioning thyroid. It is often seen during a period of illness but recovers when the illness is over. Treatment is supportive.
what is the epidemiology of hypothyroidism?
0.1-2% of adults
6 x more common in FEMALES
Most common age of onset > 40 yrs
Iodine deficiency is seen in mountainous areas (e.g. Himalayas)
what are the symptoms of hypothyroidism?
INSIDIOUS onset
Cold intolerance –> Erythema ab igne
Lethargy
Weight gain
Reduced appetite
Constipation
Dry skin
Hair loss
Hoarse voice
Mental slowness
Depression
Cramps
Ataxia
Paraesthesia
Menstrual disturbance (irregular cycles, menorrhagia), loss of libidoetc – due to prolactinaemia – get in primary hypothyroidism as increased levels of TRH causes more prolactin release
History of surgery or radioiodine therapy for hyperthyroidism
Personal/family history of other autoimmune conditions (e.g. Addison’s, type 1 diabetes mellitus)
Myxoedema coma (severe hypothyroidism usually seen in the elderly):
what are the features of a myxoedema coma?
Hypothermia
Hypoventilation
Hyponatraemia
Heart failure
Confusion - Disorientation in time and place is typical.
Coma
what are the signs of hypothyroidism?
Hands
- Bradycardia
- Cold hands
Head/Neck/Skin
- Pale puffy face
- Goitre
- Oedema
- Hair loss
- Dry skin
- Vitiligo
Chest
- Pericardial effusion
- Pleural effusion
Abdomen
- Ascites
Neurological
- Slow relaxation of reflexes
- Signs of carpal tunnel syndrome
outline the investigations for hypothyroidism?
- serum TSH- elevated
- serum T4- low
- May look for autoantibodies after TFTs are abnormal
- FBC - may show normocytic anaemia - as everything slows down so much and so does the BM production essentially/ can cause non-megaloblastic macrocytic anaemia
- U&Es - may show low sodium
- Cholesterol - may be high
what is the key investigation for hypothyroidism?
serum TSH- low
what is the management for chronic hypothyroidism?
Levothyroxine (25-200 mcg/day)
Average dosage is 125 mcg/d-> adjust dose based on clinical picture and TFTs (aim for a fT4 in upper limits without suppressing TSH)
Symptomatic improvement seen within two weeks of initiating thyroxine therapy. It may take up to six weeks of full treatment for TSH levels to normalise
Elderly pts & pts with IHD should be introduced gradually as -> precipitate in angina and palpitations - titration in small increments every 6 weeks to therapeutic dose and monitor for ischaemic symptoms
Have a blood test (TSH looked at mainly) atleast once a year to check compliance and adequacy of treatment
what should you rule out before starting thryoid hormone replacement?
adrenal insufficiency- > can precipitate addisonian crisis
thyroid hormones increase clearance of glucucorticoids
what is the management for a myxoedema coma?
Oxygen
Rewarming
Rehydration
IV T4/T3
IV hydrocortisone
Treat underlying cause (e.g. infection)
