Hyperthyroidism

RACGP exam study notes Endocrinology Hyperthyroidism

HYPERTHYROIDISM

It is a clinical syndrome that results from exposure of the body tissues to excess circulating levels of free thyroid hormones.

It is five times more common in females.

ETIOLOGY

1 . Grave’s disease – 76%

2. Multinodular goitre – 14%

3. Autonomously functioning solitary thyroid nodule – 5%

4. Thyroiditis

1. Subacute 3%

2. Postpartum

5. Drugs: amiodarone

CLINICAL FEATURES

Hyperthyroidism develops usually insidiously and most patients have had symptoms for at least 6
months before presentation.

GRAVE’S DISEASE

This is the most common cause of hyperthyroidism and is an autoimmune process in which serum IgG antibodies bind to the thyroid TSH receptors and produce stimulation of thyroid hormone production, behaving like TSH.

These antibodies are called thyroid-stimulating antibodies (TSAB).

Most patients belong to the age group 30-50 years.

Grave’s disease is distinguished clinically from other causes of hyperthyroidism by the presence of:

1- Diffuse thyroid enlargement (thyroid goiter)

2- Ophthalmopathy (eye changes)

3- Peritibial myxoedema (rare)

Most common symptoms of hyperthyroidism

1. Nervousness, irritability, tremor

2. Palpitation, dyspnea or exertion, angina

3. Weight loss, diarrhea

4. Increased sweating

5. Amenorrhea/impotence

6. Lid retraction and other* eye/ symptoms in Grave*s
disease.

CLINICAL FEATURES OF HYPERTHYROIDISM

Goiter

Diffuse + bruit
Nodular

Gastrointestinal

Weight loss despite normal or increased appetite

Diarrhea and steatorrhoea

Anorexia

Vomiting

Cardiorespiratory

Palpitations, sinus tachycardia, atrial fibrillation

Increased pulse pressure

Ankle oedema in absence of cardiac failure

Angina, cardiomyopathy, and cardiac failure

Dyspnoea on exertion

Exacerbation of asthma

EXAMINATION OF HYPERTHYROID PATIENT

General appearance

Hyperthyroid facies

Hands

Warm and sweaty palms

Tremor

Onycholysis (separation of the distal end of the nail) is also called Plummer’s nail.

Clubbing and swelling of fingers.

Arms

Pulse: tachycardia

Irregular pulse due to atrial fibrillation, high volume collapsing pulse.

Proximal myopathy.

Brisk reflexes

Neuromuscular

Nervousness

Irritability

Emotional lability

Psychosis

Tremor

Hyperreflexia, ill-sustained clonus

Muscle weakness

Proximal myopathy, bulbar myopathy

Periodic paralysis

Dermatological

Increased sweating

Pruritus

Palmar erythema, spider navi

Onycholysis

Alopecia

Pigmentation, vitiligo

Digital clubbing

Peritibial myxoedema

Reproductive

Amenorrhoea/oligomenorrhoea

Infertility

Spontaneous abortion

Loss of libido, impotence

Eyes

Exophthalmos: sclera visible below cornea.

Lid retraction: sclera visible above cornea

Conjunctiva: chemosis

Lid lag: ask the patient to follow your finger descending at a moderate rate.

The eye movements for ophthalmoplegia

Examine fundi for optic atrophy

Proptosis: look from behind and above.

Neck

Look for thyroid enlargement

Scar of surgery

Palpate thyroid

Auscultate for bruit

Pemberton’s sign –

On raising the arm above the head, patients with retrosternal goiter may develop signs of compression such as
congestion of face raised JVP, and inspiratory stridor.

Ocular

# Lid retraction, lid lag

# Grittiness, excessive lacrimation

# Chemosis

# Exophalmos, corneal ulceration

# Ophthalmoplegia, diplopia

# Papilloedema, loss of visual acuity

Other

Heat intolerance

Fatigue, apathy

Lymphadenopathy

Thirst

Osteoporosis

Chest

Gynaecomastia in males

Ejection systolic murmur

Signs of cardiac failure

Legs

Pretibia myxedema

Hyperreflexia

COMPLICATIONS

Atrial fibrillation

Periodic paralysis

Hypercalcemia and nephrocalcinosis.

Osteoporosis

Decreased libido, impotence, decreased sperm count and gynecomastia may be noted.

INVESTIGATIONS

Thyroid function tests

• Serum TSH is low

• T3, T4, and free thyroxin are raised (T3 is more sensitive for hyperthyroidism because there are occasional cases of isolated T3 toxicosis).

• TSH receptor antibody levels are usually high in Graves’ disease.

• Antithyroglobulin or anti microsomal antibodies are usually elevated in Graves’ disease.

• Serum ANA and anti- DNA are also elevated without evidence of SLE.

Thyroid radioactive iodine scan

It is performed in a diagnosed cases of thyrotoxicosis.

High radioactive iodine uptake occurs in Graves disease and toxic nodular goiter while uptake is low in subacute thyroiditis.

MRI

MR! of orbits is the imaging method of choice to visualize Graves’s ophthalmopathy.

Other investigations

• Hypercalcemia

• Increased alkaline phosphatase

• Anemia decreased granulocytes.

• Raised ESR in subacute thyroiditis.

MANAGEMENT

Following are the three methods of treatment of hyperthyroidism

1 . Antithyroid drugs

2. Subtotal thyroidectomy

3. Radioactive iodine

Strategy

Anti-thyroid drugs are first tried for patients less than 40 years, if there is relapse then consider surgery.

Radioactive iodine may be given in patients more than 40 years and those who develop recurrence after surgery.

ANTI-THYROID DRUGS

• Carbimazole ( Neo- Mercazole 5mg)

• Propylthiouracil

Mode of action

These drugs reduce the synthesis of new thyroid hormone by inhibiting the iodination of tyrosine.

Indications

The first episode of hyperthyroidism in patients of less than 40 years of age, or patients with mild thyrotoxicosis, or fear of radioactive iodine.

Side effects

Agranulocytosis (manifests as severe sore throat due to infection or unexplained fever).

Nausea, vomiting

Rash.

BETA-BLOCKERS

Propranolol

Most manifestations of hyperthyroidism are mediated via the sympathetic system; therefore beta-blockers provide rapid symptomatic control.

Beta-blockers also decrease the peripheral conversion of T4 to T3.

SURGERY

Subtotal thyroidectomy

Indications

1. Recurrent hyperthyroidism after a course of antithyroid drugs in patients of less than 40
years.

2. Initial treatment in males with large goiters and in those with severe hyperthyroidism.

3 m Poor drug compliance

Precautions

1 . Patient must be euthyroid before the operation

Complications

1 . Postoperative bleeding, laryngeal nerve palsy

2. Hypothyroidism within one year

3 . Recurrent hyperthyroidism

THYROID EYE DISEASE (Ophthalmic Grave’s disease)

There are characteristic eye features in Grave’s disease.

Proptosis & limitation of eye movements is direct effects of the inflammation, while conjunctival oedema, lid lag, and corneal scarring are secondary to the proptosis and lack of eye cover.