342382
Hyperthyroidism
- Causes
- Grave's disease: F:M: 9:1, 30-50yo,
autoimmune dis caused by stimulatory
TSH-receptor antibodies. Diffuse thyroid
enlargement, usually become hyperthyroid but
may be hypo/euthyroid. Assoc with other
autoimmune diseases.
- Toxic multinodular goitre: in elderly
and iodine def areas. Nodules that
secrete thyroid hormone.
- Toxic adenoma: solitary nodule producing
T3 and T4. On isotope scan the nodule is
'hot' and the rest of the gland suppressed.
- Others: Subacute(de Quervain's) thyroiditis: a self-limiting
viral infection with painful goitre, fever and raised ESR. Drugs:
Amiodarone, lithium (tho hypothyroidism is commoner).
Exogenous iodine: thyroxine intoxication - raised t4, reduced
T3 and thyroglobulin. Occ seen with iodine excess ie contrast
media, food contamination. Ectopic thyroid tissue: metastatic
follicular thyroid cancer, choriocarcinoma or struma ovarii
(ovarian teratoma containing thyroid tissue).
- Grave's disease: F:M: 9:1, 30-50yo,
autoimmune dis caused by stimulatory
TSH-receptor antibodies. Diffuse thyroid
enlargement, usually become hyperthyroid but
may be hypo/euthyroid. Assoc with other
autoimmune diseases.
- Features
- Symptoms: weight loss, increased
appetite, (paradoxical weight gain in
10-30%), heat intolerance, sweating,
diarrhoea, tremor, irritability, frenetic
activity, emotional lability, psychosis, itch,
oligomenorrhoea-may cause infertility.
- Signs: raised HR, AF, warm peripheries, fine tremor, palmar
erythema, hair thinning, lid lag, lid retraction, may be goitre,
thyroid nodules or bruit depending on cause.
- Features specific for Graves': exophthalmos, opthalmoplegia.
Pretibial myxoedema: oedematous swellings above lateral
malleoli, thyroid acropatchy: clubbing, painful finger and toe
swelling, periosteal reaction in limb bones.
- Complications: heart failure (esp in
elderly), angina, AF, osteoporosis,
opthalmopathy, gynaecomastia, thyroid
storm.
- Features of thyrotoxic storm: fever, agitation, confusion, coma,
tachycardia, AF, D&V, goitre, thyroid bruit, 'acute abdomen'.
Precipitents: recent thyroid surgery or radioiodine, infection, MI,
trauma.
- Symptoms: weight loss, increased
appetite, (paradoxical weight gain in
10-30%), heat intolerance, sweating,
diarrhoea, tremor, irritability, frenetic
activity, emotional lability, psychosis, itch,
oligomenorrhoea-may cause infertility.
- Investigations
- Key: Thyroid function tests: suppressed TSH, raised T3 &
T4, FBC: mild normocytic anaemia and mild leucopenia,
raised ESR, raised calcium, raised LFTs.
- Also: check thyroid autoantibodies, isotope scan
if cause is unclear to detect nodular disease or
subacute thyroiditis. If opthalmopathy test visual
fields, acuity and eye movements. In thyrotoxic
storm technetium uptake is diagnostic but do not
delay treatment for this.
- Key: Thyroid function tests: suppressed TSH, raised T3 &
T4, FBC: mild normocytic anaemia and mild leucopenia,
raised ESR, raised calcium, raised LFTs.
- Management
- Pharma: B-blockers ie propanolol for symptom control,
Anti-thyroid medication: either titration with carbimazole,
gradually reducing dose. Or block and replace with
simultaneous carbimazole and thyroxine (less risk of
hypothyroidism). In Graves' maintain on therapy for 12-18
months then withdraw, ~50% will relapse= radioiodine or
surgery.
- Carbimazole SEs: agranulocytosis =
sepsis - rare but can be
life-threatening. Warn to stop and
get urgent FBC if signs of infection.
Alternative drug: propylthiouracil.
- Carbimazole SEs: agranulocytosis =
sepsis - rare but can be
life-threatening. Warn to stop and
get urgent FBC if signs of infection.
Alternative drug: propylthiouracil.
- Radioiodine: most become hypothyroid. No evidence of
increased cancer, birth defects or infertility. CI: pregnancy
and lactation. Caution in active hyperthyroidism as risk of
thyroid storm.
- Surgery: thyroidectomy. Risk of damaging RLN:
horseness and hypoparathyroidism. Pts may
become hypo or hyperthyroid.
- Seek expert help in
pregancy/infancy.
- Thyrotoxic storm: Get expert help, give IV saline, NG tube if vomiting, take
blood for T3, T4, cultures (if suspect infection),
sedate if necessary with chlorpromazine, if no
contraindication give propanalol, high-dose digoxin,
Anti-thyroid drugs: carbimazole and after 4hrs
Lugol's solution.. IV hydrocortisone or PO
dexamethasone. Tx suspected infection with
cefuroxime. Cool with tepid sponging/paracetamol.
After 5d reduce carbimazole, after 7d stop Lugol's
solution, after 10d stop propanolol and iodine.
- Pharma: B-blockers ie propanolol for symptom control,
Anti-thyroid medication: either titration with carbimazole,
gradually reducing dose. Or block and replace with
simultaneous carbimazole and thyroxine (less risk of
hypothyroidism). In Graves' maintain on therapy for 12-18
months then withdraw, ~50% will relapse= radioiodine or
surgery.
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