Hyperthyroidism Flashcards
1
Q
Definition?
A
Hyperthyroidism is a biochemical diagnosis which occurs when there is pathologically increased thyroid hormone production and secretion by the thyroid gland
2
Q
RF?
A
- Female
- FH
- Smoking
- Low iodine intake
- Co-existing autoimmune conditions eg T1DM
3
Q
ddx?
A
- Anxiety
- Hyperadrenergic disorders
- Malignancy
- DM
- CHF
4
Q
Epidemiology
A
Age:20-30 (GD), Adenoma (30-50), multinodular goitre (>50)
Sex:Female-5:1
Prevalence: up to 3% of pop
Ethnicity:
5
Q
Aetiology
A
GD TMG SGT SLT IIH
6
Q
CP?
A
- 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
7
Q
Pathophys?
A
- 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
8
Q
Investigations first line?
A
Thyroid status examination
9
Q
I-second line?
A
• TFT's • Overt-low TSH and high T3/T4 • Subclinical-low TSH and normal T3/T4 • Test repeatedly US
10
Q
Ranges of Thormones?
A
• TSH-0.2 - 5.5 miU/L
• Free T3- 3.1 - 6.8 pmol/L
Free T4-10 - 24.5 pmol/L
11
Q
I-third line?
A
- TSH receptor antibodies-GD or preg
- ESR and CRP-thyroiditis
- Thyroid peroxidase antibodies-postpartum thyroiditis
- FBC and LFTs-anti-thyroid drugs
12
Q
I-fourth line?
A
- US with doppler
- Radionuclide thyroid uptake
- 24-hr urinary iodine excretion
13
Q
M-o/s symptomatic-first line?
A
- 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.
14
Q
M-o/s symptomatic second line?
A
- 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
15
Q
M-o/s symptomatic third line?
A
- Thyroid surgery
- Rare-large goitres, severe or failure of other methods
- Thyroidectomy
