Thyroid Disorders Flashcards
`How does hypothyroidism present?
- Weight Gain
- Cold intolerance
- Brittle nails, thin/dry skin & hair
- Hyporeflexia, slow speech
- Lethargy & low mood
- Constipation
- Bradycardia
- Heavy periods
Severe cases can cause puffy face, large tongue, hoarseness and coma
How does hyperthyroidism present?
- Weight loss
- Heat intolerance
- Muscle weakness
- Hyperreflexia
- Frequent bowel movements
- Palpitations
- Light periods
- Sweaty palms
- Thyroid eye symptoms (bulging)
- Anxiety/irritibility
How does gender affect thyroid disease?
Both hyper and hypothyroidism are much more common in women
What are the types of Hypothyroidism?
Primary
Subclinical
Secondary
What causes congenital Hypothyroidism?
- developmental problems e.g. agenesis
- Dyshormogenensis (autosomal recessive condition preventing TH production)
What causes acquired Primary Hypothyroidism?
- Autoimmune (hashimoto’s) thyroiditis
- Iatrogenic
- Chronic Iodine Deficiency
- Post-subacute thyroiditis
What can cause secondary or tertiary hypothyroidism?
- Pituitary tumours
- Craniopharyngioma
- Pituitary surgery/radiotherapy
- Sheehan’s Syndrome
- Isolated TRH deficiency
What is Sheehan’s Syndrome?
Post-partum ischaemic necrosis of the pituitary due to blood loss/hypovolaemic shock of childbirth
Its a potential cause of secondary hypothyroidism
List some iatrogenic causes of primary hypothyroidism?
Post op
Radioactive Iodine or Anti-Thyroids
Amiodarone (Sub-acute thyroiditis)
RT for H/N cancer
What tests would you run for suspected hypothyroidism?
- TFTs i.e. TSH & fT4
- Anti-Thyroid Peroxidase Antibodies (Hashimotos)
- FBC
- Lipids
- Serum Na+
- Muscle enzymes, ALT & CK
- Prolactin
Explain why youd do each test for hypothyroidism?
FBC - Raised MCV (RBC size) Lipids - Hypercholesterolaemia Na+ - Hyponatremia due to excess ADH from hypothyroidism Muscle enzymes, ALT & CK are all raised Prolactin - Hyperprolactinaemia
How will TFT’s Appear for each class of Hypothyridism?
Primary - Low fT4 but high TSH
Secondary - Low fT4 & low or normal TSH
Subclinical - Normal fT4 & High TSH
What do we use to manage hypothyroidism?
Levothyroxine (T4) tablets
Explain the dosing of Levothyroxine?
Start at 50mcg/day
Titrate up to 100mcg/day after 2 weeks
Keep increasing until their TSH (primary disease) or fT4 (Secondary Disease) is normal.
What special cases affect how you use Levothyroxine?
- IHD needs to be started lower and titrated slowly as it can trigger Angina
- Pregnant women need more T4
- Myxedema Coma needs IV T3
- Post-partum Thyroiditis needs to have the meds removed for 6 weeks and TFTs measured to see when it abates
Should we treat subclinical hypothyroidism?
Only if:
- TSH >10
- > 5 + Antibodies
- TSH elevated + symptoms (temporary trial therapy for symptom improvement)
- Pregnant or planning pregnancy
What are the risks of levothyroxine?
- Thyrotoxicosis
- AF
- Osteopenia
How does Goitre occur in hypothyroidism?
No fT4
No -ve feedback
Excess TSH
Hyperstimulation -> Hyperplasia of Thyroid gland
What are the causes for Primary hyperthyroidism?
Graves Disease - 70%
Toxic Multinodular Goitre - 20% (Plummers Disease)
Thyroid Adenoma
Subacute Thyroiditis
Solitary Toxic Thyroid Nodule (benign adenoma)
What is Grave’s Disease?
Autoimmune condition in which TSH receptor antibodies continuously stimulate the thyroid causing PRimary hyperthyroidism
What is Toxic Multinodular goitre?
Multinodular Goitre producing excess thyroid hormones
Whats the main cause of secondary hyperthyroidism?
Pituitary Adenoma producing TSH
What is Thyrotoxicosis without hyperthyroidism?
Where you get excess thyroid hormone without hyperthyroidism.
Due to exogenous thyroxine or destructive thyroiditis causing stores of thyroid hormones to be released
What causes destructive thyroiditis?
Post-partum
Amiodarone induced
Most common causes
How do you diagnose Hyperthyroidism?
Based on the presentation and TFTs
Can do TSH receptor antibody test for Grave’s Specifically
Describe how hyperthyroidism TFTs appear?
Primary - High fT4 & low TSH
Secondary - High fT4 & High TSH
Subclinical - Normal fT4 & low TSH
How is Hyperthyroidism treated?
1st) Anti-thyroid Drugs (ATDs)
2nd) Radioiodine
Resection of thyroid or pituitary adenoma
How are anti-thyroid drugs used?
Carbimazole or Propylthiourcil
A titration regimen for 12-18 months then move on to radioiodine if uncured
How is Radioiodine used?
For hyperthyroidism
USed after ATDs fail
High dose ablative regimen cures 90% of patients but leaves 70% hypothyroid
When would we treat Subclinical hyperthyroidism?
If:
- Elderly
- Persistant subclinical hyperthyroidism
- High cardiac risk patient
Risks of Hyperthyroidism treatments?
ATDs can cause a rash and agranulocytosis which is a rare and potentially fatal complication
Radioiodine makes ~70% of patients hypothyroid and can cause eye disease
How would you investigate a goitre?
- TFTs
- Isotope scabn
- US
- FNA
- CXR for retrosternal extension
IF you suspect cancer a serum calcitonin to rule out MEdullary Thyroid Cancer
What are the main types of thyroid cancer?
Most common:
Papillary
Follicular
Others:
Anaplastic
Lymphomas
Medullary Carcinoma
How do Differentiated Thyroid Carcinomas spread?
Papillary carcinomas spread to local lymph nodes
Follicular Carcinomas metastasise to lung/blood/bone
What is medullary thyroid cancer?
Cancer of C cells in the thyroid gland
Produces calcitonin
Associated with MEN 2
Treatments for Thyroid cancers?
High Dose radioiodine
Long-Term levothyroxine to suppress the tumour
Lymphoma - External RT/chemo
Anaplastic - Can be delayed with external RT
Thyroidectomy - Only treatment that works on medullary thyroid cancer
When would we stop Levothyroxine for Thyroid cancer?
Withdraw from the thyroxine for 2 weeks as a trial and do a full body radioisotope scan to see if its all gone
Features of Thyroid Storm
Acute severe associated with untreated hyperthyroidism:
Pyrexia
Tachycardia
Delerium
What is De Queverns Thyroiditis
Viral infection - Neck tenderness/pain -Dysphagia -Hyperthyroidism Often self limiting with supportive care
Presentations of Graves
Exophthalmos
Pretibial myxedema
Diffuse Goitre
Presentation of Toxic Multinodular Goitre
Firm nodules on palpation