Hypothyroidism

Question 1

Background

Answer 1

Hypothyroidism comes from under production and secretion of thyroid hormones.

Question 2

Types and causes

Answer 2

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:
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, tumours, surgery to pituitary, radiotherapy, or trauma. TSH levels badly low or normal but FT4 lower than range.

Question 3

Signs & Symptoms

Answer 3

• Fatigue,
• Weight gain,
• Constipation,
• Menstrual irregularities,
• Depression,
• Dry skin,
• Cold intolerance,
• Reduced body and scalp hair
• Fluid retention

Question 4

Diagnosis

Answer 4

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.

Question 5

Treatment

Answer 5

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 avoid doses causing TSH suppression or thyrotoxicosis.
- 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 occasions 3 months apart - Levothyroxine (LT4).
If still got symptoms with normal TSH then adjust dose avoid doses causing TSH suppression or thyrotoxicosis.
TSH high or untreated for long TSH level can take 6 months to be normal.
MONITOR: SAME AS ABOVE

IF SYMPTOMATIC <65 BUT <10 mlU/L on 2 separate occasions 3 months apart = 6 MONTH TRIAL Levothyroxine (LT4).
monitoring the same.
When symptoms stop with TSH in range consider stopping.

Secondary:
Refer urgently to endocrinologist to asses underlying cause.

IN PREGNANCY:
Refer all females 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. IF pregnant measure TFT and discuss starting or changes to treatment + TFT monitoring with endocrinologist whilst waiting to review. reduces risk of obstetric and neonatal complications.

Question 6

Signs of over treatment

Answer 6

Tachycardia, nervousness, tiredness, headache, increased excitability, sleeplessness, tremors and possible angina

Question 7

Complications

Answer 7

Dyslipidaemia, coronary heart disease, HF, impaired fertility, pregnancy complications, impaired concentration and/or memory, and rarely myxoedema coma (life-threatening medical emergency).