Hypothyroidism

Question 1

What is myxoedema?

Answer 1

Clinical effect of lack of thyroid hormone.

It is common (4/1000/year).

Question 2

Symptoms of myxoedema

Answer 2

Tiredness 
Sleepy 
Lethargic 
Decreased mood 
Cold intolerance
Weight gain 
Constipation 
Menorrhagia 
Hoarse voice 
Decreased memory/cognition 
Dementia 
Myalgia 
Cramps 
Weakness

Question 3

Signs of myxoedema

Answer 3

Bradycardia 
Reflexes relax slowly 
Cerebellar ataxia 
Dry thin hair/skin 
Yawing/drowsy/coma 
Cold hands 
Ascites + non-pitting oedema (lids, hands, feet) 
Pericardial or pleural effusion 
Round puffy face 
Defeated demeanour 
Immobile

Question 4

Diagnosis of myxoedema

Answer 4

Increased TSH, Reduced T4 (Primary)

Decreased T4, Decreased TSH (Secondary)

Question 5

Causes of myxoedema

Answer 5

Primary atrophic hypothyroidism (common. diffuse lymphocytic infiltration of the thyroid, leading to atrophy hence no goitre)
Hashimoto’s thyroiditis (Goitre due to lymphocytic and plasma cell infiltration. Commoner in women aged 60-70 years)
Iodine deficiency (developing world)
Post-thyroidectomy or radioiodine treatment
Drug-induced: Antithyroid drugs, iodine, lithium and amiodarone.
Secondary hypothyroidism- hypopituitarism (very rare)

Question 6

What is amiodarone?

Answer 6

This is an iodine-rich drug that causes hypothyroidism due to toxicity from iodine excess.
Hypothyroidism can be caused by toxicity from iodine excess (T4 release is inhibited).
Thyrotoxicosis may be caused by destructive thyroiditis causing hormone release. Here, radioiodine uptake can be undetectable and if this is the case, glucocorticoids may help.
Get expert help.
Thyroidectomy may be needed if amiodarone cannot be discontinued. T1⁄2 of amiodarone ≈80d, so problems persist after withdrawal.
If on amiodarone, check TFTS 6-monthly.

Question 7

Treatment for hypothyroidism?

Answer 7

Healthy and young:
Levothyroxine (T4), 0–100mcg/24h PO; review at 12wks. Adjust 6-weekly by clinical state and to normalize but not suppress TSH (keep TSH >0.5mU/L). Thyroxine’s t1⁄2 is ~7d, so wait ~4wks before checking TSH to see if a dose change is right.
NB: small changes in serum-free T4 have a logarithmic effect on TSH. Once normal, check TSH yearly.
Enzyme inducers increase the metabolism of levothyroxine.
• Elderly or ischaemic heart disease:
Start with 25mcg/24h; increase the dose by 25mcg/4wks according to TSH (cautiously, as levothyroxine may precipitate angina or MI).
• If the diagnosis is in question and T4 already given: Stop T4; recheck TSH in 6 weeks.

Question 8

Which conditions are linked with hypothyroidism?

Answer 8

Seen with other autoimmune diseases (type 1 DM, Addison’s, and PA).
Turner’s and Down’s syndromes
Cystic fibrosis
Primary biliary cholangitis
Ovarian hyperstimulation (OHCS p311)
POEMS syndrome—polyneuropathy, organomegaly, endocrinopathy, an m-protein band (plasmacytoma) + skin pigmentation/tethering.
Genetic: Dyshormonogenesis: genetic (often autosomal recessive) defect in hormone synthesis, eg Pendred’s syndrome (with deafness): there is increased uptake on isotope scan, which is displaced by potassium perchlorate.

Question 9

Complications of myxoedema

Answer 9

Myxoedema coma- this is the ultimate hypothyroid state before death.