Primary and Secondary Hyperthyroidism Flashcards
(11 cards)
What is primary hyperthyroidism?
- An overactive thyroid gland
- Hyperthyroidism is associated with excess levels of unbound thyroid hormones in the peripheral circulation, leading to a hypermetabolic state - many of the body’s processes are abnormally increased.
- Both T4 and T3 levels are usually elevated, but in a small subset of hyperthyroid patients only T3 is elevated (T3 toxicosis).
What are the signs and symptoms of hyperthyroidism?
Very numerous again! Many non specific
* Increased appetite,
* Weight loss
* Anxiety
* Restlessness
* Insomnia
* Fatigue
* Heat intolerance
* Sweating
* Diarrhoea,
* Fine tremor
* Menstrual disturbance
* Tachycardia
* Arrhythmia
* Systolic hypertension
* Goitre
* Thyroid bruit
* Exophthalmos (assoc. with hyperthyroidism due to Grave’s disease)
* Pretibial myxoedema (assoc. with hyperthyroidism due to Grave’s disease)
What causes hyperthyroidism?
- Autoimmunity: Grave’s disease (Most common cause in iodine-sufficient countries)
- Subacute thyroiditis - inflammation of thyroid gland
- Toxic adenoma - benign tumour made of thyroid hormone secreting hormones
- Multinodular goitre - thyroid is full of nodules full of thyroid hormone producing cells
- Excess iodine intake
- Excess intake of levothyroxine during treatment for hypothyroidism
- Taking the drug Amiodorone (which is used to treat cardiac arrhythmia)
What is Grave’s disease?
- Also known as diffuse toxic goitre
- The most common cause of primary hyperthyroidism in iodine-sufficient countries
- An autoimmune process in which thyroid stimulating antibody (TSAb), (also known as TSI, Trab, or LATS), binds with the TSH receptor on the thyroid, stimulating it to over produce thyroid hormones and to increase in size resulting in a goitre.
- Elevation of TSAb is present in 60-80% of cases and is diagnostic for Grave’s disease.
- Grave’s disease may be associated with a palpable diffuse goitre( rather than a nodular goitre) and general signs and symptoms of hyperthyroidism (as previously described).
What other conditions are related to hyperthyroidism - 1?
OPHTHALMOPATHY - Specific to Grave’s disease
* Occurs in 50% of cases.
* Autoimmune-mediated inflammation of the tissues of the retro-orbital space (behind the eyes) causes exophthalmos (proptosis). People have a ‘staring expression’ before protruding eyeballs
DERMOPATHY
* Specific to autoimmune thyroiditis.
* Auto-immune mediated inflammation of the dermis causes non-pitting oedema, thickening of the skin and erythema and, without pain or pruritus.
TOXIC MULTINODULAR GOITRE - 15-20% of cases of thyrotoxicosis
* More prevalent in areas of iodine deficiency.
* More common in elderly individuals, particularly those with a long-standing goitre.
* Associated with mild symptoms of hyperthyroidism, a slight elevation of thyroid hormones, negative TSI (thyroid stimulating antibodies) and low or absent anti-TPO antibodies.
What other conditions are related to hyperthyroidism - 2?
TOXIC ADENOMA
* A toxic adenoma is a single hyperfunctioning follicular thyroid adenoma - benign tumour.
* Toxic adenoma accounts for 3-5% of thyrotoxicosis (hyperthryoidism) cases.
* The excess thyroid hormone suppresses TSH levels.
* It is associated with low or absent anti-TPO and negative TSI antibodies.
SUBACUTE THYROIDITIS - 15-20% of cases of hyperthyroidism
* Inflammatory condition, presents with low grade fever, tenderness and enlargement of the thyroid gland, weakness & possible symptoms of hyperthyroidism early in the course of the disease which may progress to hypothyroidism.
* May be post-partum or triggered by illness; post-viral, (measles mumps, influenza, EBV, covid-19).
* Usually resolves in 2-7 months.
* Associated with raised ESR (marker for inflammation), and in some
cases, anti-TPO and/or anti-TG antibodies
What are the risk factors for developing hyperthyroidism?
- A family history of thyroid disease.
- A history of other autoimmune conditions (such as pernicious anaemia, coeliac
disease, type 1 diabetes, SLE, rheumatoid arthritis, Sjögren’s syndrome, vitiligo). - Pregnancy and post-partum
- Excessive iodine intake from iodine-containing medicines or supplements
- Being assigned female at birth (ratio 1:7-8)
- Age 30-60 (Grave’s disease)
What are common tests and investigations for hyperthyroidism?
Clinical investigations:
* Observation of signs such as restlessness, excessive sweating, fine tremor, exophthalmos (eye bulging or proptosis), lid retraction and lid lag.
* Palpable diffuse goitre (Grave’s disease) or thyroid nodules (Toxic multinodular goiter)
* Tachycardia and/or arrhythmia, systolic hypertension, possible thyroid bruit (if you listen, due to increased circulation)
* Examine the lower legs for signs of pretibial myxoedema which is assoc. with Grave’s disease
Thyroid specific blood tests
* Elevated levels of T4 and/or T3
* Suppressed levels of TSH (high levels of thyroid hormones reduce pituitary secretion of TSH due to negative feedback)
* Elevated levels of TSAb also known as TSI, TRAb, or LATS (in Graves disease only)
* Other markers of thyroid autoimmunity, such as anti-TG) antibodies or antithyroperoxidase (anti-TPO) antibodies may be present in Grave’s disease, even though they have no major role in the aetiology of the condition
Other blood tests
* High ferritin (due to the effect of thyroid hormones on ferritin synthesis)
* Hypocholesterolaemia, low triglyceride, low folate (due to the increased metabolic state)
* High blood calcium levels (due to altered bone metabolism)
* High sex hormone-binding globulin (SHBG) (due to increased oestrogen levels).
Further investigations
* Iodine-123 (123I) scanning (scintigraphy ) to establish the pattern of radioactive Iodine uptake
* ECG
What is secondary hyperthyroidism?
- Secondary hyperthyroidism is not due to a problem with the thyroid itself, but
to a problem with the pituitary gland (such as a pituitary tumour), which
secretes high levels of TSH, triggering increased T4 production by the thyroid. - TSH-secreting tumours do not respond to negative feedback from increasing T4 or T3 levels, therefore high levels of T4 and T3 are associated with High TSH
- It is important to ensure that both TSH and T4 are tested, since high T4, and normal or high TSH, suggest pituitary rather than thyroid disease,
- Central hyperthyroidism may be missed by only measuring levels of TSH, stimulating
hormone. Basic TSH test alone is very common these days and can lead to incorrect diagnosis
What are the complications of hyperthyroidism?
- Cardiac hypertrophy (heart enlargement), cardiac arrhythmia, stroke, heart failure - all due to increased pressure on the heart
- Osteoporosis - due to increased bone turnover
- Life-threatening thyrotoxic crisis (thyroid storm)
- Increased risk of thyroid cancer
- Ophthalmopathy and/or dermopathy (with Grave’s disease)
What is conventional treatment for Hyperthyroidism?
- Antithyroid medications (e.g.carbimazole) for approximately 18 months. (increases risk of diabetes)
- Beta blockers to reduce symptoms
- Radioiodine therapy (usually leads to hypothyroidism & can worsen ophthalmopathy)
- Thyroidectomy (for very large goitre or where radioactive iodine is contraindicated due to ophthalmopathy or pregnancy)
- Oral steroids for ophthalmopathy
- Topical steroids for myxoedema
