Hypothyroidism.

Normal levels.

  • TSH 0.5 to 5.0
  • FT4 10 to 22

Common.

15 per 1000 females.

F > M by 14.

Middle aged.

5% +.

Causes.

  • Auto-immune (Hashimotos).
  • Idiopathic atrophic.
  • Post surgery.
  • Post radiation.
  • Iodine deficiency – commonest worldwide.
  • Congenital
  • Thyroiditis – later stages.
  • Over treatment.
  • Meds = amiodarone, lithium.
  • Secondary to pituitary or hypothalamic failure.

Symptoms.

Very varied.

  • Vague tiredness, depression, myalgia.
  • Weight gain despite loss of appetite.
  • Cold intolerance.
  • Constipation
  • Coarse dry skin and hair.
  • Loss of outer 1/3 of eyebrows.
  • Only 1/3 of elderly patients have classical signs.

Signs.

  • Bradycardia
  • Cerebellar signs.
  • Hypotension
  • Goitre
  • Carpal tunnel syndrome.

Diagnosis.

TSH is test of choice.

  • TSH ­ raised
  • FT4¯ suppressed

Thyroglobulin antibodies + in Hashimotos.

Check LDL also

Do ECG.

Associated conditions.

Autoimmune.

  • Type 1 DM.
  • Pernicious anaemia.
  • Addisons
  • Premature ovarian failure.
  • Vitiligo

Anaemia.

High LDL.

Do not test TSH when acutely unwell, early pregnancy or post any op as DTSH level.

Refer.

  • Young – will need lifelong follow up.
  • Pregnant or post partum.
  • Pituitary disease.
  • Very unwell.
  • Anyone with problems after starting treatment.

 

Note on Hashimotos.

  • Middle aged females.
  • Usually hypo with goitre.
  • Other auto-immune conditions.

Note on congenital hypothyroidism.

  • 1 per 4000.
  • Test by heel prick.
  • Due to agenesis usually.
  • In –utero gets T4 transplacentally.
  • Treat within 2 weeks of birth.
  • Normal IQ reached in most.

Cretinism occurs when severe maternal T4 deficiency.Not improved by neonatal supplements.

Treatment.

  • Lifelong thyroxine (T4).
  • Treat the TSH.
  • Check TSH every 4-6 weeks until stable –takes this long to readjust.
  • Will take up to one year to see full benefits.
  • Check TSH yearly to prevent under-treatment.
  • In elderly start at 50mcgs.
  • In IHD start at 50mcgs alt days. Risk of MI if treat too fast. Risk of A. Fib if over treat.
  • In others can start at 100mcgs.
  • May be given twice a week if tolerated.
  • If on T4 due to a thyroid carcinoma, the TSH should be ZERO.
  • May need to increase dose if pregnant or on Phenytoin or CMZ.

Stopping treatment?

  • 28% on it when may not be necessary, esp, after recovery of Hashimotos or thyroiditis.
  • Half the thyroxine and in 2/12 check TFTs.
  • If TSH not rising can stop thyroxine and check TFTs again in 2/12.
  • If not rising can stay off thyroxine but yearly TFTs needed.


 Subclinical hypothyroidism.

  • Mildly elevated TSH.
  • Normal FT4.
  • Up to 10% of females over 60 have TSH from 5 –6.
  • Check if have anti-thyroid antibodies.
  • If have antibodies and TSH increase 4.3% a year progress.
  • If have TSH increase alone 2.6% will progress.
  • Males less likely to have it but more likely to progress.
  • More likely to progress if over 60.
  • More likely to progress with higher levels of TSH.

Advantages to treating.

  • Prevents progression to overt hypothyroidism.
  • May help reverse symptoms.
  • Improvement in IHD?
  • Prevent loss to follow up.

Disadvantages.

  • Cost
  • May lead to hyperthyroidism –A.Fib, no evidence for osteoporosis.

Treat if:

  • Antibodies +.
  • If goitre.
  • If deterioration in TFTs in 6/12.
  • ?symptomatic

If high LDL?

Check TFTs in 6/12 if not treating.

Acceptable not to treat if no antibodies and TSH less than 10, but recheck in 6/12.