Hypothyroidism

Question 1

Hypothyroidism

Answer 1

Thyroid hormone (thyroxine [T4] + tri-iodothyronine [T3]) deficiency

Question 2

What are the subtypes of hypothyroidism?

Answer 2

Primary: Overt + Subclinical
Secondary (central)

Question 3

What is primary hypothyroidism?

Answer 3

Thyroid hormone deficiency due to thyroid gland being unable to produce thyroid hormones because of iodine deficiency or an abnormality within the gland itself

Question 4

What is subclinical hypothyroidism?

Answer 4

TSH: high
T3+T4: normal

Question 5

What is secondary hypothyroidism?

Answer 5

Thyroid hormone deficiency as a result of insufficient thyroid stimulation due to a pituitary or hypothalamic disorder

Question 6

5 causes of primary hypothyroidism

Answer 6

AI thyroiditis (most common in UK)
Iodine deficiency (most common cause worldwide)
Post-ablative therapy/ surgery
Drug therapy
Subacute (de Quervain’s)

Question 7

What is Hashimoto’s thyroiditis?

Answer 7

AI thyroiditis a/w goitre

Question 8

Describe the epidemiology of hypothyroidism

Answer 8

1-2% F in UK
F > M

Question 9

List 3 drugs that can cause hypothyroidism

Answer 9

Lithium
Amiodarone
Anti-thyroid drugs e.g. Carbimazole

Question 10

What occurs subacute thyroiditis/ postpartum thyroiditis?

Answer 10

Transient thyroiditis
Initial brief hyperthyroidism followed by longer period hypothyroidism

Question 11

List 3 conditions associated with Hashimoto’s thyroiditis

Answer 11

T1DM
Addisons
Pernicious anaemia

Question 12

List 8 S/S of hypothyroidism

Answer 12

Weight gain
Lethargy
Cold intolerance
Constipation
Menstrual irregularities/ sub fertility
Carpal tunnel syndrome
Dry skin
Hair loss

Question 13

Investigations for hypothyroidism

Answer 13

FBC: a/w pernicious anaemia
TFTs
HbA1c: a/w T1DM
Coeliac serology
Serum lipids
Thyroid antibody testing

Question 14

Describe TFTs in hypothyroidism

Answer 14

High TSH
Low T3 + T4

Question 15

What antibodies may be detected in hypothyroidism?

Answer 15

Thyroid peroxidase antibodies (TPOAb)
TSH receptor antibodies (TRAbs)

Question 16

What drug is used in treatment of hypothyroidism? How should it be taken?

Answer 16

Levothyroxine sodium
Take on empty stomach in morning before food

Question 17

Describe the clinical effects of levothyroxine

Answer 17

Sx may lag behind Tx changes for several weeks or months

Question 18

Describe monitoring in hypothyroidism

Answer 18

Recheck TSH every 3 months after initiation
Adjust dose according to Sx + TFTs
Once 2 similar measurements 3 months apart, check annually

Question 19

What is the starting dose of levothyroxine?

Answer 19

50-100 micrograms OD

If cardiac disease, severe hypothyroidism or >50: initial starting dose should be 25mcg OD with dose slowly titrated

Question 20

How does levothyroxine dosing change during pregnancy?

Answer 20

Increase dose by at least 25-50 micrograms
(increased demands during pregnancy)

Question 21

List 4 side effects of levothyroxine therapy

Answer 21

Hyperthyroidism: due to over Tx
Reduced bone mineral density
Worsening of angina
Atrial fibrillation

Question 22

Which drugs cause reduced absorption of Levothyroxine?

Answer 22

Iron
Calcium carbonate

Question 23

List 7 complications of untreated hypothyroidism

Answer 23

Dyslipidaemia
Metabolic syndrome
Coronary heart disease
Stroke
Heart failure
Infertility
Decreased taste, vision + hearing

Question 24

What is a life-threatening complication of hypothyroidism? How may this present?

Answer 24

Myxoedema coma
Presents with
Lethargy
Bradycardia
Hypothermia
Seizures
Coma

Question 25

What may precipitate myxoedema coma?

Answer 25

Heart failure
Sepsis
Stroke