Thyroid Conditions

Hypothyroidism

This is a common condition characterised by a lack of thyroid hormone.

The issue is that it gives non-specific symptoms which are very subtle, and so can be tricky to diagnose. However, if treated, the prognosis is excellent.

Symptoms are mostly related to the magnitude of the thyroid hormone deficiency

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

Management

Levothyroxine (hormone replacement therapy) to replace T4.

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

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

Hashimoto thyroiditis

This is the most common cause in areas with sufficient iodine.

It occurs due to autoimmune destruction of thyroid gland.

Antithyroglobulin and antithyroid peroxidase antibodies are usually present.

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

It causes chronic inflammation, a risk factor for developing cancers like lymphoma.

It is more common in postmenopausal women (60–70).

Iodine deficiency

Iodine is needed to make thyroid hormone (most common cause worldwide)

Primary Atrophic Hypothyroidism

This is a condition where there is diffuse lymphocyte infiltration of the thyroid gland.

This leads to thyroid gland atrophy, hence does not give a goitre.

Riedel fibrosing thyroiditis

This is a chronic inflammatory disease which causes fibrosis of the thyroid gland.

It leads to hypothyroidism with a hard, nontender thyroid gland. 

Drugs 

Antithyroid drugs e.g., lithium, amiodarone (can cause either hypo/hyperthyroidism).

Subclinical Hypothyroidism

This occurs when T4 levels are normal amidst raised TSH levels.

It is common and associated with a risk of progression to hypothyroidism.

For these patients, it is advisable to recheck the TSH after 2–4 months to confirm that levels are still raised.

It is only treated if TSH levels are very high or there is presence of thyroid antibodies suggesting that autoimmune disease is present. 

Sick Euthyroid Syndrome

This is a condition which usually occurs in acute systemic illness.

It leads to low levels of TSH, T4 and T3 (T3 levels are especially low).

However, TSH levels can be within the normal range.

Levels usually correct with recovery from illness and usually no treatment is needed.

Hyperthyroidism

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

It leads to an increase in the basal metabolic rate and sympathetic nervous activity (due to upregulation of 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

Management

It is important to stabilise the heart as well as treat the underlying cause

Beta-blockers, e.g., propranolol is used to slow down the heart rate

Antithyroid medication e.g., PUT/carbimazole

Radioiodine can be used

Thyroidectomy is a surgical option if medical treatment is unsuccessful

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

Graves’ disease 

This is an autoimmune condition which is the most common cause of hyperthyroidism.

There is production of IgG antibodies which are directed towards the TSH receptor stimulating thyroid release. Anti-thyroid peroxidase antibodies can also be present.

It usually occurs in women of childbearing age (30–50 years).

Symptoms

Diffuse goitre as constant TSH receptor stimulation leads to thyroid hyperplasia

Pretibial myxoedema – shin fibroblasts express TSH receptor causing inflammation

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

Key tests

Bloods tests show high T4, low TSH, high glucose, low cholesterol

Multinodular goitre

This is an enlarged thyroid gland with multiple nodules. The regions can become TSHindependent, leading to uncontrolled T4 release, which leads to hyperthyroidism.

It can be managed with radioactive iodine therapy.

Toxic adenoma

This is a solitary nodule producing excess thyroid hormone.

Iodine scan shows that the nodule is “hot” (hormone producing) compared to the rest of the gland which is suppressed.

This will likely require surgical management to remove the benign tumour.

Ectopic thyroid tissue

In metastatic follicular thyroid cancer, metastasis can produce T₃/T₄

Subacute (De Quervian) Thyroiditis

This is a subacute granulomatous thyroiditis after a viral infection.

It initially presents as a tender thyroid with a goitre giving a transient hyperthyroidism.

The patient can then become euthyroid (stage 2) and finally hypothyroid (stage 3).

It is self-limiting and the thyroid function eventually returns to normal.

Thyroid scintigraphy shows globally reduced iodine-131 (and raised ESR).

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).

Symptoms

Lump in neck, hoarseness of voice (if large)

Key tests

US to visualise nodule, biopsy gives definitive diagnosis, CT/MRI for staging

Management

Surgery, e.g., total thyroidectomy followed by radioiodine to kill the residual cells and reduce the chances of recurrence (with adjuvant chemo/radiotherapy)

Papillary carcinoma

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

It is usually discovered as an asymptomatic nodule that appears as a neck mass.

It is non-thyroid hormone secreting, so patients are euthyroid.

It is well-differentiated, slow-growing, and localised, although it can metastasise. 

Follicular carcinoma

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

Medullary carcinoma 

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

Anaplastic carcinoma

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