Hypothyroidism Flashcards
(7 cards)
Background
Hypothyroidism comes from under production and secretion of thyroid hormones.
Types and causes
Primary -
Comes from thyroid gland. can caused by Iodine deficiency, autoimmune disease (Hashimotos thyroiditis), Radiotherapy, Surgery or drugs.
Primary more common in females.
Primary can be either overt or subclinical:
- Overt - TSH above range FreeT4 below range,
- Subclinical - TSH above range but Free T3 and T4 within range. In pregnancy = overt if above TSH levels. free T4 dont matter.
Causes of primary:
Tumours, surgery, radiotherapy, or trauma.
Autoimmune - body recognises the thyroid tissues as foreign antigens and a chronic immune reaction ensues, resulting in lymphocytic infiltration of the gland and progressive destruction of functional thyroid tissue
Postpartum - Can get lymphocytic thyroiditis in 2-10 months after birth. Hypothyroid state can be followed by thyrotoxic state. Postpartum Hypothyroidism usually transient (2-4 months) and need short treatment with LT4. These patients can be increased risk of permanent hypothyroidism
Subacute granulomatous - Inflammatory or viral infection cause with transient hyperthyroidism then transient hypothyroidism.
Iatrogenic - Causative agents: hyperthyroidism treatments, Lithium, Amiodarone.
Secondary - caused by a pituitary or hypothalamic disorder. TSH levels badly low or normal but FT4 lower than range.
Signs & Symptoms
- Fatigue,
- Weight gain,
- Constipation,
- Menstrual irregularities,
- Depression,
- Dry skin,
- Intolerance to cold
- Reduced body and scalp hair
- Fluid retention
Diagnosis
Primary: Suspect if they show >1 signs.
Secondary: Primary features + Possible features of hypothalamic pituitary disease - recurrent headache, diplopia, and/or visual field defects.
Postpartum thyroiditis (PPT): Usually 3-8 months postpartum last 4-6 months.
Assessment:
Ask on:
- symptoms
- Current or recent pregnancy
- Current or recent non thyroidal illness
- Drugs i.e. amiodarone, lithium or OTC supplements biotin.
- Risk factors= Family/personal history of thyroid or autoimmune disease, history of down syndrome or iodine deficiency, OR previous radiotherapy to head or neck
- Ask on causes of 2ndy hypo…
EXAMINE:
- Signs or complications
- Thyroid enlargement
- Signs of other autoimmune disease
PERFORM TFT - see if TSH above range. (refer to background to see what results could mean)
- Can do extra blood test, Serum thyroid peroxidase test, Ultrasound of neck.
Treatment
Aim: Alleviate symptoms, Sort TFT levels, Reduce risk of complications
Primary overt:
1st line - Levothyroxine (LT4) takes 3-5 days then levels off in 4-6 weeks. need to get TSH level normal if still got symptoms with normal TSH then adjust dose.
- Patient with long term untreated condition or very high TSH can take 6 months
MONITOR: TSH every 3 months until stable THEN ANUALLY. If still symptomatic monitor FreeT4.
Subclinical:
Look at underlying conditions.
IF TSH =/>10 mIU/L on 2 separate times 3 months apart - Levothyroxine (LT4).
Still symptoms with normal TSH then adjust dose.
TSH high or untreated for long TSH level can take 6 months to be normal.
MONITOR: SAME AS ABOVE
IF SYMPTOMATIC <65 BUT <10 on 2 separate times 3 months apart = 6 MONTH TRIAL Levothyroxine (LT4).
monitoring the same.
When symptoms stop with TSH in range consider stopping.
Overt/Sub clinical - for levo avoid doses causing TSH suppression or thyrotoxicosis.
Secondary:
Refer urgently to endocrinologist to asses underlying cause.
IN PREGNANCY:
Refer all pregnant or trying to be.
Can advise to delay conception if TFT not in range until stable on Levothyroxine.
TFT results use trimester related results if already pregnant.
- measure TFT and discuss starting/changes to treatment + TFT monitoring whilst waiting to review.
LEVO DOSE MAY BE INCREASED but monitor more carefully as levo can pass placenta and harm foetus.
- monitor b4 pregnancy, at each trimester and after birth.
Safe in breastfeeding
Signs of over treatment
Tachycardia, nervousness, tiredness, headache, increased excitability, sleeplessness, tremors and possible angina
Complications
Dyslipidaemia, coronary heart disease, HF, impaired fertility, pregnancy complications, impaired concentration and/or memory, and rarely myxoedema coma (life-threatening medical emergency).
