Hyperthyroidism Flashcards
What is hyperthyroidism
hyperthyroidism refers to the symptoms caused by excessive amounts of circulating thyroid hormone.
Classic sx are FASHIP fatigue anxiety significant weight loss despite an increased appetite heat intolerance increased perspiration palpitations
Groups of Causes of hyperthyroidism (4)
1) hyper functioning of the thyroid gland
- increased production of thyroid hormones and increased expression of their effects
2) Destruction of the thyroid gland
- releases thyroid hormones stored in thyrocytes
3) Exogenous hyperthyroidism
- excess intake of thyroid hormones from outside the body
4) Ectopic (extrathyroidal) hormone production
- thyroid hormone production from the body outside of the thyroid gland
5)) excess total thyroid hormones in circulation d/2 increased TBG production
Causes of increased thyroid function causing thyrotoxicosis
Graves disease (∼ 60–80% of cases)
Toxic multinodular goiter (MNG) (∼ 15–20% )
Toxic adenoma (3–5% of cases)
TSH-producing pituitary adenoma (thyrotropic adenoma)
β-hCG mediated hyperthyroidism (sim structure to TSH) (hydatidiform mole, choriocarcinoma)
Hashitoxicosis
Conditions causing damage to the thyroid gland and the release of thyroid hormone
subacute thyroiditis
- Subacute granulomatous thyroiditis/deQuervain’s thyroiditis
- Subacute lymphocytic thyroiditis/post-partum thyroiditis
Drug-induced thyroiditis (amiodarone, lithium)
Hashimoto’s thyroiditis
Radiation thyroiditis
Palpation thyroiditis after surgery of parathyroid gland
Conditions causing ectopic thyroid hormone production
Struma ovarii: ovarian teratoma in which the endoderm differentiates into thyroid tissue and releases thyroid hormones
Metastatic thyroid follicular carcinoma:Malig neoplasia of the follicular cells that metastasise and release thyroid hormones wherever they settle
PP of hyperthyroidism
1) Disorders of the thyroid gland → excess production of T3/T4 → compensatory decrease of TSH
2) Thyrotroph adenoma → ↑ TSH levels → ↑ T3/T4 levels
3) Excess intake/ectopic thyroid hormone production → ↑ levels of circulating T3/T4 → compensatory decrease of TSH
Majority of sx are caused by the thyroid hormones causing an increase in beta receptors on the cell surface membrane potentiating the action of SNS
Gem sx of hyperthyroidism
Goiter
Graves opthalmopathy
- Bilateral exophthalmos
- lid retraction
- Diplopoda
- conjunctival hyperaemia
Heat intolerance & excessive sweating (moist, warm skin) d/2 vasodilation and increased BMR
Weight loss despite increased appetite
increased frequency of bowel movements & diarrhoea
Weakness, fatigue
Hyperreflexia
CDV dx in hyperthyroidism ( most prevalent in the elderly)
Tachycardia: almost all cases
Palpitations, irregular pulse (due to atrial fibrillation/ectopic beats)
Hypertension with a widened pulse pressure
Cardiac failure sx in elderly
-pedal edema, dyspnea on exertion
Musculoskeletal sx in hyperthyroidism
Fine tremor of the outstretched fingers
Myopathy with muscle weakness in pts > 40
Osteopathy: osteoporosis , fractures (in the elderly)
suggests long term hyperthyroidism
Reproductive as sx in hyperthyroidism
Increased levels of serum sex hormone-binding globulin (SHBG)
Women:
Causes low unbound estradiol concentrations
Reduced estrogen synthesis
-amenorrhea
-infertility
Men: low unbound testosterone concentrations plus increased extragonadal conversion of testosterone to estradiol. -gynecomastia -reduced libido -erectile dysfunction
Dg of hyperthyroidism
LAB
1) Thyroid function tests
- TSH levels 1st line: TSH is low/undetectable
- β-hCG peak at the end of 1st trimester → decrease in serum TSH levels
- Free T3 /T4 levels: both are characteristically high
2) thyroglobulin (exogenous hyperthyroidism is suspected ):characteristically low levels
3) Serum thyroid antibodies: (Graves disease/Hashimoto thyroiditis)
IMAGING 1) thyroid US -I sting of choice in PREGNANCY -shows structure and can indicate cause of hyperthyroidism #enlargement #nodules #vascularisation
Thyroid scintigraphy (shows thyroid uptake of radioactive iodide) -CI in pregnancy
Principle of thyroid sctintigraphy
Only the functional part of the gland takes up RAI.
Normal thyroid tissue: normal sized gland with a diffuse uptake of RAI.
Most common findings
Graves disease: enlarged gland with diffusely increased RAI uptake
Toxic MNG:
- multiple nodular areas,
- both cold and hot,
- resulting in an overall heterogeneous appearance
Toxic adenoma:
-a hot nodule
Factitious hyperthyroidism:
-no uptake of RAI since there is no thyroid gland hyperfunction.
Dx of hyperthyroidism
Neuro sx : panic attack’s
Hyper adrenal sx:Drug intoxication p: cocaine/ amphetamines
Heart failure/ arrhythmia
