Hyperthyroidism Flashcards
Definition?
Hyperthyroidism is a biochemical diagnosis which occurs when there is pathologically increased thyroid hormone production and secretion by the thyroid gland
RF?
- Female
- FH
- Smoking
- Low iodine intake
- Co-existing autoimmune conditions eg T1DM
ddx?
- Anxiety
- Hyperadrenergic disorders
- Malignancy
- DM
- CHF
Epidemiology
Age:20-30 (GD), Adenoma (30-50), multinodular goitre (>50)
Sex:Female-5:1
Prevalence: up to 3% of pop
Ethnicity:
Aetiology
GD TMG SGT SLT IIH
CP?
- Heat intolerance
- Sweating
- Weight loss increased appetite
- Diarrhoea
- Fatigue
- Onycholysis
- Pretibial myxoedema
- Lid lag/retraction
- Graves ophthalmopathy- exophthalmos, periorbital oedema
- Goitre
- Tachycardia, palpitations, HT, HF, pain and irregular rhythms
- Tremor, myopathy, osteopathy
- Oligo/amenorrhoea, infertility, bleeding, ED, low libido
- Anxiety/depression, irritability, insomnia, hyperreflexia
Pathophys?
- Excess thyroid hormones
- Thyrotoxicosis-overproduction form thyroid gland
- Normally
- Hypothalamus detects low levels of thyroid hormones and releases TRH into hypophyseal portal system to ant. pituitary
- TSH releases and stimulates follicular cells convert thyroglobulin into T3 and T4 and release them
- These travel in the blood bound to plasma proteins and are taken up by cells
- T4 is converted into T3-increased metabolic rate, CO, bone reabsorption and increased SNS
- Too much thyroid hormone-hypermetabolic state
- GD- AI disorder-B cells produce antibodies against thyroid proteins (thyroid-stimulating immunoglobulins) that bind to receptors on follicular cells mimicking TSH-excess thyroid hormones
- Toxic nodular goitre-follicles start generating more thyroid hormone-mutated TSH receptor keeping cells active
- Adenoma-benign tumour producing excess hormone
- Thyroiditis-release of hormones in inflammation/infection
- Jod-Basedow syndrome-iodine deficient person gets escalated dose of iodine
- Neonatal-new-borns of mothers with GD start making too much thyroid hormone to meet previous levels-response to thyroid-stimulating immunoglobulins crossing the placenta
• Secondary -thyroid makes a lot of thyroid hormones as ectopic TSH tumour in ant-pituitary
Investigations first line?
Thyroid status examination
I-second line?
• TFT's • Overt-low TSH and high T3/T4 • Subclinical-low TSH and normal T3/T4 • Test repeatedly US
Ranges of Thormones?
• TSH-0.2 - 5.5 miU/L
• Free T3- 3.1 - 6.8 pmol/L
Free T4-10 - 24.5 pmol/L
I-third line?
- TSH receptor antibodies-GD or preg
- ESR and CRP-thyroiditis
- Thyroid peroxidase antibodies-postpartum thyroiditis
- FBC and LFTs-anti-thyroid drugs
I-fourth line?
- US with doppler
- Radionuclide thyroid uptake
- 24-hr urinary iodine excretion
M-o/s symptomatic-first line?
- Refer or ED admission if symptoms of complication or specialist investigations/management
- Beta blocker
- Anti-thyroid drugs-carbimazole, Propylthiouracil (preg)
- Titration-block regime — the dose is adjusted regularly depending on free thyroxine (FT4) measurements. A dose reduction may be needed if the FT4 level falls to low-normal or below the reference range, or the TSH level increases, indicating the development of hypothyroidism. The aim is to titrateto the lowest dose needed to maintain a euthyroid state.
- Block and replace regime — the antithyroid drug blocks the synthesis of thyroid hormone. The FT4 level is monitored and levothyroxine (LT4) is added in when the FT4 is in the reference range. Adjustments to the LT4 dose are made to maintain FT4 levels in the reference range.
M-o/s symptomatic second line?
- Radioactive iodine ablation
- Destruction of thyroid tissue sing radioactive (iodine 131) through sodium/iodine symporter
- Not if preg, cancer,young,severe GD
- Pre-treatment methimazole-less complications
- Single-dose isotope uptake by thyroid gland-emits B radiation that slowly destroys thyroid tissue
M-o/s symptomatic third line?
- Thyroid surgery
- Rare-large goitres, severe or failure of other methods
- Thyroidectomy
M-subclinical?
follow up
2WW
M-GD first line?
- ATD
- Beta-blocker
- Radioactive iodine
- Orbitopathy management-CS (methylprednisolone), supportive therapy
- Dermopathy management-topical CS
- Surgery
- Post-therapy hormone replacement
M-thyroid storm?
- High dose ATD
- CS
- BB
- Iodine solution
- Colestyramine- reduces enterohepatic circulation of thyroid hormones
- Lithium
M-follow-up?
Monitor bloods-6 wks during and 3-6 months after
Prognosis?
- Overt-risk of recurrence is 20-30%
- Subclinical-risk of occurrence to overt in 4 yrs-5-8%
- GD-prognosis worse in smoker and higher AB concs
- Post-partum-up to 64% into overt
Complications?
- Graves orbitopathy
- Thyroid storm-severe hypermetabolism
- If stops treatment, infection and has surgery
- Compression
- Paralysis
- AF
- HF
- Osteoporosis
- Death
- Mood disorders
- Miscarriage, pre-eclampsia, IUGR, death, fetal complications