Thyroid Conditions

Thyroid conditions involve under/activity of the gland. To determine cause, number of test you can do. Thyroid function should be checked in people with AF + diabetes + hyperlipidemia + patients on amiodarone/lithium

 

a) Hypothyroidism (myxoedema)

This is a condition marked by a lack of thyroid hormone which is fairly common. If treated, the prognosis is excellent, but the problem is the it gives non-specific symptoms which are very subtle.

– Features are based on decreased BMR and decreased sympathetic activity

 

Symptoms:

– Increased weight with normal appetite

– Cold intolerance with no sweating

– Bradycardia

– Decreased mood

– Constipation

– Tiredness and lethargic

– Poor memory/cognition

Signs:

– Slow reflexes and ataxia

– Cold dry hands

– Ascites/oedema

– Hypercholesterolemia

– Heavy Periods (menorrhagia)

– Absent Reflexes

– Carpal Tunnel Syndrome

Whilst these are the general signs of a lack of thyroid hormone, there are a number of different causes:

  • Hashimoto thyroiditis – most common cause in regions where iodine levels are adequate

– Due to autoimmune destruction of thyroid gland, associated with HLA-DR5

– It is associated with other autoimmune conditions e.g. – Type I diabetes, Addison’s.

– Antithyroglobulin and antithyroid peroxidase antibodies present

– Gives chronic inflammation with germinal centres and Hurthle cells

– More common in postmenopausal women (60-70) and presents with firm non-tender goitre

 

  • Primary Atrophic Hypothyroidism

– A diffuse lymphocyte infiltration of thyroid leading to atrophy, hence does not give a goitre

 

  • Riedel fibrosing thyroiditis – chronic inflammatory disease with fibrosis of thyroid gland

– Gives hypothyroidism with a hard, nontender thyroid gland

 

  • Iodine deficiency – this is needed to make thyroid hormone (most common cause worldwide)

 

  • Drugs – Antithyroid drugs e.g. lithium + amiodarone (can cause either hypo/hyperthyroidism)

 

  • Secondary Hypothyroidism – This is secondary to low TSH due to hypopituitarism, very rare

 

  • Subclinical Hypothyroidism – This occurs when T4 levels are normal amidst raised TSH levels

– It is common (10% of people above 55 years) with risk of progression to hypothyroidism

– Advisable to recheck TSH after 2-4 months to confirm that levels are actually raised

– Only treated in TSH > 10 or thyroid antibodies or other autoimmune disease present

 

  • Sick Euthyroid Syndrome – This is a condition which usually occurs in acute systemic illness

– Theoretically everything TSH, T4 and T3 is low but the TSH can be within the normal range

– T3 are especially low in these types of patients

– Changes are reversible with recovery from illness and usually no treatment is needed

 

Hypothyroidism treatment: Levothyroxine – hormone replacement therapy to replace T4

      – Iron supplements reduce absorption of levothyroxine so give these 2 hours apart

 

  • Myxoedema Coma – This is one of the biggest complications of untreated hypothyroidism is a:

            – This is the ultimate hypothyroid state before death, resulting from severe absence of thyroid hormone

 

Symptoms: Exceptionally hypothyroid features –> Hypothermia + Bradycardic + Coma + Seizures

                           – Low BP + low glucose + hyporeflexia

 

Treatment – Give IV liothyronine (T3) + Hydrocortisone (+ fluids/glucose if required)

 

b) Hyperthyroidism

This is a condition marked by increased levels of circulating thyroid hormone.

– It leads to increase in basal metabolic rate (due to increased synthesis of Na/K-ATPase)

– Increased sympathetic nervous system activity (due to increased B1-adrenergic receptors)

Symptoms: 

– Weight loss despite increase appetite

– Heat intolerance and sweating

– Tachycardia + palpitations

– Tremor/anxiety

– Diarrhoea

– Decreased muscle mass with weakness

– Bone resorption with hypercalcemia

– Hyperglycaemia

Signs:

– Fast pulse/atrial fibrillation

– Warm moist skin

– Thin hair

– Staring gaze with eyelid lag

– May be goitre

– Hypocholesterolaemia

– Low/absent periods

 

 

Whilst these are the general signs of excess thyroid, there are a number of different causes:

  • Graves’ disease – An autoimmune condition which is the most common cause of hyperthyroidism

– Autoimmune IgG antibody stimulates the TSH receptor increasing thyroid release

– TSH stimulating antibodies seen in 90% and anti-thyroid peroxidase antibodies also present

– Usually occurs in women of childbearing age (30-50 years)

 

Specific symptoms:

– Diffuse goitre as constant TSH stimulate leads to thyroid hyperplasia

– Pretibial myxoedema – shin fibroblasts express TSH receptor causing inflammation

– Exophthalmos (bulging of eyes) – fibroblasts behind orbit express the TSH receptor

– Stimulation leads to increased inflammation and oedema, seen in 30% of patients

– If inflammation involves the cornea, becomes very concerning.

– Stopping smoking aids eye symptoms

 

Diagnosis: TFT shows high T4, low TSH.  High glucose and hypocholesterolaemia

 

  • Multinodular goitre – This is an enlarged thyroid gland with multiple nodules, seen in elderly

– Regions become TSH-independent giving hyperthyroidism

Diagnosis – Nuclear scintigraphy shows a patchy uptake

Treatment – Radioiodine therapy

 

  • Toxic adenoma – This is a solitary nodule producing excess thyroid hormone.

– Iodine scan shows nodule is “hot” (hormone producing) and rest of gland suppressed

 

  • Ectopic thyroid tissue – in metastatic follicular thyroid cancer, metastasis can produce T3/T4

 

  • Subacute (De Quervian) Thyroiditis – A subacute granulomatous thyroiditis after a viral infection

– Presents as a tender thyroid with a goitre giving a transient hyperthyroidism (stage 1)

– Patient then becomes euthyroid (stage 2) before hypothyroidism (Stage 3)

– Self-limiting and function eventually returns to normal

Diagnosis – Thyroid scintigraphy shows globally reduced iodine-131 (+ Raised ESR)

 

Hyperthyroidism treatment – We first try to stabalise the heart and then treat the cause.

i) Beta-blockers – e.g. Propranolol gives control of symptoms due to high sympathetic activity

ii)Antithyroid medication – Methimazole + PUT

iii) Radioiodine

iv) Thyroidectomy – risk of recurrent laryngeal nerve injury + people become hypothyroid after

 

  • Hyperthyroid Crisis (Thyroid Storm) – One of the biggest complications of hyperthyroidism

            – High levels of T4 ultra-sensitise the body to the sympathetic system resulting in serious symptoms

            CausesThyroid surgery, trauma, acute iodine load (e.g. CT contrast)

            SymptomsHeat generation (T >38.5), Tachycardia, Confusion, Hypertension + Heart failure

            Treatment – IV propranolol + Propylthiouracil + Dexamethasone (stops T4 –> T3) + Iodine solution

 

c) Thyroid cancer

Thyroid nodules are more likely to be benign. Malignant cancers are characterized by iodine uptake test and are cold, showing decreased uptake and then require biopsy performed by fine needle aspiration (FNA).

 

  • Papillary carcinoma (MOST COMMON)

This is the most common thyroid carcinoma, usually in young females.

– Exposure to radiation in childhood is risk factor

– Made of papillae lined by cells with clear “Orphan Annie eye” nuclei + papillary projections

– The patient is completely euthyroid however

 

Management – Total thyroidectomy –> followed by radioiodine to kill residual cells

                                 – Yearly thyroglobulin levels to detect recurrent disease

 

  • Follicular carcinoma (2nd MOST COMMON)

A malignant proliferation of follicular cells producing thyroid hormone, seen in middle age

– Appears to be encapsulated, but microscopically capsular invasion in seen which differentiates in from a follicular adenoma

– Metastasises early via the blood to the bones and lungs

– Can produce exogenous thyroid hormone giving symptoms of hyperthyroidism

 

Management – Total thyroidectomy –> followed by radioiodine to kill residual cells

                                 – Yearly thyroglobulin levels to detect recurrent disease

 

  • Medullary carcinoma (3rd MOST COMMON)

A Malignant proliferation of C cells which secrete calcitonin

– Familial cases are seen due to multiple endocrine neoplasia MEN2A (glands) and 2B (involves oral mucosa) associated with mutations in the RET oncogene

– Calcitonin gets deposited in tumour as amyloid and may give hypocalcaemia

– Metastasises to both lymph nodes and through blood

 

Management – Thyroidectomy + lymph node clearance

 

  • Anaplastic carcinoma (LEAST COMMON)

An undifferentiated malignant tumour usually seen in elderly females

– Causes local invasion of structures giving pressure symptoms

– Not responsive to treatment, so palliation is offered with surgery and radiotherapy

d) Congenital thyroid conditions

  • Thyroglossal duct cyst

This is a cystic remnant of the thyroglossal duct.

– Thyroid tissue develops at the base of the tongue and travels down along duct to neck

– Although it usually degenerates, it can persist and dilate

– Presents as a neck mass in the anterior triangle which moves upwards with tongue protrusion due to the residual connection with the back of the tongue

– Can become painful if infected

 

Management – Surgical excision

 

  • Lingual thyroid

This is the presence of thyroid tissue at the base of tongue

– Can interrupt with swallowing/breathing if large or asymptomatic

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