Hypothyroidism Flashcards
What is another name for this?
Myxoedema
Causes - Autoimmune:
Hashimoto’s thyroiditis:
- Why do they get a goitre?
- What sex is it commoner in?
- What age group is it commoner in?
Primary atrophic hypothyroidism:
- Why do they atrophy instead of a goitre?
60-70 yrs
Due to lymphatic and plasma cell infiltration
Female
Diffuse lymphocytic infiltration of the thyroid, leading to atrophy
Diffuse. 1. (dĭ-fūs´) not definitely limited or localized. 2. (dĭ-fūz´) to pass through or to spread widely through tissue or substance.
Causes:
What deficiency could cause this?
Why does this deficiency cause a goitre?
Iatrogenic causes? - 2
Drug-induced:
- How does lithium for BD cause hypoT?
- How does amiodarone cause hypoT?
Iodine deficiency
Radioiodine Rx
Post thyroidectomy
——
Lithium induces a decrease in the production of thyroxine (T4) from the thyroid gland, as well as interference with the de-iodination of T4 to T3 (tri-iodothyronine, the metabolically active form of thyroid hormone).
its direct toxic effect on the thyroid - it can also cause hyper T
Symptoms:
Systemic - 3
Dermatological - 6
THEY GET HYPERTENSION (MAINLY DIASTOLIC)
Fatigue
Cold
Weight gain
Dry skin Itch Brittle hair Hair loss Coarse features Oedema
Symptoms:
GI - 1
Gynae - 1
Neuro - 2
Constipation
Menorrhagia
Weakness - proximal or global
Impaired memory/cognition
Symptoms:
3 symptoms due to compression by goitre?
Dysphagia
SOB +/- stridor
Hoarseness
Signs - Neck:
Hashimoto’s - how does the goitre feel? Is it tender?
What other cause has a goitre?
Other causes have no goitre
Firm
Iodine deficiency
Signs:
BRADYCARDIC mneumonic
Bradycardia
Reflexes relax slowly
Ataxia (cerebellar)
Dry thin hair/skin
Yawning/drowsy/coma
Cold hands
Ascites, non-pitting oedema,
pericardial/pleural effusion
Round puffy face
Defeated demeanour
Immobile bowel, ileus - constipation
CHF, Carpal tunnel syndrome
Signs:
BRADYCARDIC mneumonic:
Why does it cause tiredness?
Why does it cause cold hands?
Why do they get oedema?
Why do they get carpal tunnel syndrome?
Since your body’s energy production requires certain amounts of thyroid hormones, a drop in hormone production leads to lower energy levels, causing you to feel weak and tired.
Same as above
It is thought that fibroblast stimulation by the TSH receptor increases the deposition of glycosaminoglycan, which results in osmotic oedema and fluid retention. It is thought that many cells responsible for forming connective tissue react to increases in TSH levels
Severe, untreated hypothyroidism can cause fluid buildup that puts pressure on the nerves in your arms and legs. This can lead to tingling, pain, and numbness where the nerve is damaged. Low thyroid can sometimes lead to carpal tunnel syndrome, which affects the nerves in your hand and wrist.
Investigations:
What do TFT’s show?
No need to check T3.
What will you find in secondary (pituitary) hypothyroidism?
What 2 tests can be done in autoimmune thyroid disease?
When is the only time TSHR-Ab needs to be checked?
What does subclinical hypothyroidism mean?
TSH high
T4 low
Low TSH and T4 - due to lack of TSH from the pituitary gland
TPO-Ab - raised in autoimmune disease
If there is thyroid eye disease - as it is this antibody that leads to the disease
They have symptoms but blood test doesn’t hit criteria for needing Rx
Investigations:
Why do women tend to have iron-deficiency anaemia?
Cholesterol and triglycerides are measured as they can be raised. Why is this?
Due to menorrhagia
As thyroid hormone levels are low (hypothyroidism), your body doesn’t break down and remove LDL cholesterol as efficiently as usual. LDL cholesterol can then build up in your blood. Thyroid hormone levels don’t have to be very low to increase cholesterol.
Management:
Main Rx?
How often is TSH checked once stable?
Should the dose be increased or decreased in pregnancy?
Levothyroxine (T4)
Annually
Increased as demand is increased (DUH - its pregnancy)
Levothyroxine:
How long does it take to work?
Is it taken with or without food?
Can it be taken with other drugs?
Cautions - why is it started low and titrated up in the elderly?
Several wks
Titrate up every 2-3 months
No - same reason it isn’t taken with food - it may interfere with absorption - same as rifampicin
MI risk especially those with IHD
Complications:
What is the main serious complication?
Chronic:
- Why does it cause heart disease and eventual failure?
- Why does it cause dementia?
Myxoedema coma
Hypothyroidism can result in decreased cardiac output, increased systemic vascular resistance, decreased arterial compliance, and atherosclerosis. Impaired cardiac muscle relaxation, decreased heart rate, and decreased stroke volume contribute to heart failure in hypothyroidism.
Hypothyroidism may cause deterioration of cognitive ability because TH is needed to help regulate the brain glucose-consuming processes for neurotransmission, memory, and other higher functions.
Complications:
In pregnancy?
Eclampsia
Anaemia
Prematurity
SGA baby
