THYROID DISEASE

Question 1

WHAT IS THE FUNCTION OF THYROID HORMONES?

Answer 1

1) Basal metabolic rate
2) Thermogenesis
3) Gluconeogenesis and glycogenolysis
4) Control heart rate

Question 2

BRIEFLY OUTLINE THE HYPOTHALAMIC- PITUITARY- THYROID AXIS?

Answer 2

1) TRH released by hypothalamus in response to low TH
2) TRH acts on anterior pituitary to release TSH
3) TSH acts on thyroid gland driving T3 and T4 secretion

Question 3

WHAT ARE THE CAUSES OF HYPERTHYROIDISM?

Answer 3

1) Auto- immune (Grave’s disease) - presence of TSH receptor stimulating antibodies
2) Thyroiditis - inflammation of the thyroid gland
3) Thyroid nodules - autonomous secretion of T3/T4 from solitary toxic nodule
4) Medication - amiodarone

Question 4

WHAT ARE THE SYMPTOMS OF HYPERTHYROIDISM?

Answer 4

1) Weight loss with increased appetite
2) Heat intolerance
3) Sweating
4) Palpitations
5) Irritability/ anxiety

Question 5

WHAT ARE THE SIGNS OF HYPERTHYROIDISM?

Answer 5

1) Tachycardia - fast and irregular heartbeat
2) Tremor
3) Exophthalmos - grave’s disease
4) Goitre - enlarged thyroid
5) Warm peripheries
6) Lid-lag

Question 6

WHAT ARE THE INVESTIGATIONS OF HYPERTHYROIDISM?

Answer 6

1) Blood test - TSH, serum free or total T3, serum free or total T4, TSH receptor stimulating antibodies

Question 7

WHAT IS THE HALLMARK TEST RESULTS FOR HYPERTHYORIDISM?

Answer 7

• elevated free T4 and T3 with undetectable TSH

Question 8

WHAT IS TEST RESULT FOR T3-TOXICOSIS?

Answer 8

• elevated free T3, normal free T4 and supressed TSH

Question 9

WHAT IS THE TEST RESULT FOR SUBCLINICAL HYPERTHYROIDISM?

Answer 9

• normal free T3 and T4 with suppressed TSH

Question 10

WHAT IS THE PHARMACOLOGICAL TREATMENT FOR HYPERTHYROIDISM AND WHEN IS IT USED?

Answer 10

• Thionamides - carbimazole and propylthiouracil (act as preferred substrate for iodination by thyroid peroxidase, reducing T3 and T4 synthesis)
• Used as 1st line approach in preparation for definitive treatment, inducing remission or when definitive treatment is declined.

Question 11

HOW LONG DOES IT TAKE FOR RESULTS TO NORMALISE AFTER DRUG TREATMENT INITIATION?

Answer 11

• 4-6 weeks

Question 12

WHAT ARE THE SIDE EFFECTS OF THIONAMIDES?

Answer 12

• Agranulocyotosis (bone marrow suppression), unexplained fever or sore throat requires urgent blood test to exclude pancytopenia (deficiency of RBC, WBC and platelets). If neutrophil count is low then drug must be stopped.

Question 13

WHAT ARE THE 2 DEFINITIVE TREATMENT FOR HYPERTHYROIDISM?

Answer 13

1) Radioactive iodine - cause DNA damage leading to death of thyroid cells causing reduce thyroid function. Involves administration of single dose iodine. Can cause hypothyroidism requiring life long thyroxine treatment, avoid contact for 2 weeks due to still emitting radiation
2) Thyroidectomy- most effective, used when patient can’t do radiation therapy. Complication include damage to RLN, damage to parathyroid gland.

Question 14

WHAT IS PRIMARY HYPOTHYROIDISM AND ITS CAUSES?

Answer 14

Low thyroid hormone levels due to problem with thyroid gland itself

1) Autoimmune (Hashimoto’s) - attacks thyroid gland
2) Iodine deficiency - neonates
3) Drugs - amiodarone
4) Iatrogenic - surgery and radioiodine

Question 15

WHAT IS SECONDARY HYPOTHYROIDISM AND ITS CAUSE ?

Answer 15

TSH deficiency due to hypothalamic-pituitary disease

Question 16

WHAT ARE THE CLINICAL FEATURES OF HYPOTHYROIDISM?

Answer 16

1) Weight gain
2) Cold intolerance
3) Fatigue
4) Constipation
5) Bradycardia
6) Thickening of skin
7) Puffiness around the eyes

Question 17

WHAT ARE THE SYMPTOMS OF HYPOTHYROIDISM SIMILAR TO?

Answer 17

Depression and chronic fatigue

Question 18

WHAT ARE THE INVESTIGATION OF HYPOTHYROIDISM?

Answer 18

1) Serum TSH
2) Serum free T4
3) Thyroid peroxidase antibodies - autoimmune hypothyroidism

Question 19

WHAT IS THE TEST RESULT FOR HASHIMOTO’S HYPOTHYROIDISM?

Answer 19

• positive thyroid peroxidase antibodies

Question 20

WHAT IS THE RESULT FOR PRIMARY HYPOTHYROIDISM?

Answer 20

• low free T4 and elevated TSH

Question 21

WHAT IS THE RESULT FOR SECONDARY HYPOTHYROIDISM?

Answer 21

• non-elevated TSH and low T4

Question 22

WHAT IS THE TREATMENT FOR HYPOTHYROIDISM?

Answer 22

1) Thyroxine replacement - improve symptoms and normalise thyroid function

Question 23

WHAT DOES ELEVATED TSH DESPITE HYPOTHYROIDISM TREATMENT INDICATE?

Answer 23

• poor compliance

- malabsorption (coeliac)

Question 24

WHAT IS THE MANAGEMENT FOR SUBCLINICAL HYPOTHYROIDISM?

Answer 24

• If asymptomatic, treatment is not needed as thyroid function can spontaneously go back to normal
• If TSH>10 even if patients asymptomatic then start thyroxine as high chance of progression to hypothyroidism.