Hypothyroidism

Question 1

prognosis

Answer 1

if treated - excellent

if not, disastrous - heart disease, dementia

one must be alert to subtle, specific symptoms

Question 2

classification

Answer 2

primary - disease of gland itself

Question 3

myoxedema

Answer 3

severe hypothyroidism - medical emergency

Question 4

subclinical hypothyroidism

Answer 4

high levels of TSH, but normal levels of fT4

often a precursor to developing overt hypothyroidism

Question 5

cretinism

Answer 5

hypothyroidism in babies - condition of dwarfism and limited mental functioning due to the deficiency of thyroid hormones present at birth

often owes to maternal hypothyroidism

Question 6

hair and skin features

Answer 6

coarse, sparse hair

expressionless face

periorbital puffiness

pale, cool doughy skin

vitiligo may be present

hypercarotenaemia - yellow pigmentation of the skin

Question 7

thermogenesis

Answer 7

cold intolerance

cold hands

Question 8

fluid symptoms

Answer 8

pitting oedema - fluid retention

Question 9

cardiac

Answer 9

reduced heart rate

cardiac dilatation

pericardial effusion

worsening of heart failure

Question 10

metabolic

Answer 10

hyperlipidaemia - xanthelasma

decreased MR: decreased appetite and weight gain

Question 11

xanthelasma

Answer 11

cholesterol deposits around the eyes

Question 12

gi

Answer 12

constipation

rarely, megacolon and intestinal obstructionand ascites

Question 13

respiratory

Answer 13

deep, hoarse voice

macroglossia

obstructive sleep apnoea

Question 14

neurology

Answer 14

decreased intellectual and motor activities

lowered memory and cognition

depression, psychosis

peripheral neuropathy

carpal tunnel sydrome

decreased visual acuity

prolongation of tendon jerks eg reflexes relax slowly

Question 15

muscles

Answer 15

muscle stiffness and cramps

Question 16

gynae/reproductive

Answer 16

menorrhagia (abnormally heavy/prolonged bleeding)

later, oligomenorrhoea or amenorrhoea

hyperprolactinaemia

Question 17

prolactin

Answer 17

hormone that enables females to produce milk

inc TRH causes inc PRL secretion

Question 18

causes of self limiting primary hypothyroidism

Answer 18

withdrawal of anti thyroid drugs

subacute thyroiditis with transient hypothyroidism

post partum thyroiditis

Question 19

causes of non goitrous primary hypothyroidism

Answer 19

atrophic thyroiditis

post ablative surgery (radioiodine, surgery)

post radiotherapy to neck

congenital developmental defect

Question 20

causes of goitrous primary hypothyroidism

Answer 20

iodine deficiency

drug induced eg amiodarone, lithium

hasimotos thyroiditis

Question 21

iodine deficiency

Answer 21

dietary iodine deficiency still exists in some areas where goitre is common

patients may be euthyroid or hypothyroid depending on the severity

the mechanism is thought to be borderline hypothyroidism (lack iodine, cant synthesise MIT or DIT) leading to TSH stimulation and thyroid gland enlargment (even though it cant produce/secrete any hormone)

Question 22

Hashimoto’s Thyroiditis

Answer 22

autoimmune destruction of the thyroid gland and subsequent reduced thyroid hormone production

Question 23

what is the most common cause of hypothyroidism

Answer 23

Hashimoto’s Thyroiditis

Question 24

epidemiology of Hashimoto’s Thyroiditis

Answer 24

family history of auoimmune thyroiditis or other autoimmune disorders

more common in women

Question 25

pathophysiology of Hashimoto’s Thyroiditis

Answer 25

* antibodies attack **thyroid peroxidase**, which is an enzyme used in the production of thyroid hormones (**TPO antibodies are present in very high titres)** * antibodies can also attack the thyroglobulin leading to destruction of the follicular cells of the thyroid - anti-Tg antibodies * T cell infiltration and inflammation produces a **goitre**

Question 26

what is the thyroid gland like in Hashimoto’s Thyroiditis

Answer 26

goitre * firm and rubbery * may range from soft to hard

Question 27

thyroid status in Hashimoto’s Thyroiditis

Answer 27

either

Question 28

causes of secondary hypothyroidism

Answer 28

rare usually widespread deficiency or loss of function of either the hypothalamus or pituitary gland (not enough TSH produced) causes include infiltration, infection and malignancy

Question 29

management of hypothyroidism

Answer 29

replacement therapy of thyroid hormones normal MR should be restored gradually, so as not to precipitate cardiac arrhythmias analogue of T4 - **levothyroxine** - is given for life

Question 30

what is the starting dose of levothyroxine

Answer 30

depends on the severity of the condition, less in the elderly dose is gradually increased so as to avoid causing cardiac arrhythmias etc TSH levels should be checked every 2 months after any dose change and once the dose is stabilised, every 12-18 weeks

Question 31

what is the dose of levothyroxine titrated to

Answer 31

fT4 level, as in secondary hypothyroidism TSH is not produced normally so is unreliable as a marker

Question 32

when should levothyroxine be taken

Answer 32

before bed

Question 33

dose requirements for levothyroxine in pregnancy

Answer 33

increase by 25-50% (usually 25mcg) as soon as pregnancy is suspected as thyroxine hormones are vital to the development of the baby

Question 34

myxoedema coma

Answer 34

the ultimate hypothyroid state before bed mortality 60% despite early diagnosis and treatment

Question 35

who does myxoedema coma usually affect

Answer 35

elderly women with long standing but frequently unrecognised/untreated hypothyroidism

Question 36

ECG findings of myxoedema coma

Answer 36

bradycardia low voltage complexes varying degrees of heart block (heart failure) T wave inversion prolongation of QT interval

Question 37

other findings in myxoedema coma

Answer 37

goitre type 2 respiratory failure: hypoxia, hypercapnia, respiratory acidosis, cyanosis coma and seizures adrenal failure psychotic - myxoedema madness seen just before coma

Question 38

treatment of myxoedema coma

Answer 38

ABCDE actively rewarm (blankets, fluids), aiming for a slow rise in body temperature cardiac monitoring for arrhythmias close montoring of urine output, central venous pressure, blood sugars, oxygenation broad spectrum antibiotics thyroxine cautiously, hydrocortisone for the first hour

Question 39

clinical features of Hashimoto's thyroidits

Answer 39

* **Goitre**: the gland is usually firm and rubbery but may range from soft to hard. * Patients may be **hypothyroid** or euthyroid. * Anti-thyroid peroxidase and also anti-Tg antibodies