Goitre – Disease, Treatment, Thyroid Notes

Goitre

Definition: Diffuse enlargement of the thyroid gland is described as goitre. (It is derived from the Latin word, Guttur = the throat.)

Classification Of Goitre

Simple goitre

• Puberty goitre
• Colloid goitre

• Iodine-deficiency goitre
• Multinodular goitre

Toxic goitre

• Graves’ disease
• Secondary thyrotoxicosis in MNG
• Solitary nodule
• Other causes

Neoplastic goitre

• Benign adenoma (follicular adenoma)
• Malignant tumours: They are further classified into the following:

Read And Learn More: Clinical Medicine And Surgery Notes

1. Primary

• Well-differentiated carcinoma
  • Papillary carcinoma
  • Follicular carcinoma
• Poorly differentiated carcinoma
  • Anaplastic carcinoma
• Arising from parafollicular cells
  • Medullary carcinoma
• Arising from lymphatic tissue
  • Malignant lymphoma

2. Secondary (Metastasis)

• Malignant melanoma, renal cell carcinoma, and breast carcinoma produce secondaries in the thyroid due to blood spread.

Thyroiditis

• Granulomatous thyroiditis
• Autoimmune thyroiditis Riedel’s thyroiditis

Other rare causes of Goitre

• Acute bacterial thyroiditis
• Thyroid cyst
• Thyroid abscess
• Amyloid goitres.

However, multinodular goitres, solitary nodules, malignant goitres, and puberty goitres are common causes of goitres. Bacterial thyroiditis is rare. Riedel’s thyroiditis is very very rare.

Multinodular Goitre

• Multinodular goitre is the end-stage result of diffuse hyperplastic goitre. Excessive metabolic demands cause an excessive enlargement of the thyroid. Therefore common in women.
• Metabolic demands increase during puberty. A goitre appearing during that period is called puberty goitre. A goitre can develop during pregnancy and is called pregnancy goitre. Both of them are physiological but eventually may develop into multinodular goitre (MNG).

Aetiopathogenesis

Multinodular goitre results due to a continuous stimulation by the TSH which is released from the anterior pituitary.

1. Puberty goitre, pregnancy goitre
   • Seen in girls at puberty or during pregnancy when the metabolic demands are high and the production of T₃, and T₄ are comparatively normal. Due to the feedback mechanism, TSH levels increase, which stimulates the thyroid gland and causes diffuse hypertrophy and hyperplasia.
   • This is also called physiological goitre and can be treated by giving tablet thyroxine (T4) 0.2 mg/day to suppress TSH.
   • Goitre may disappear if treatment is given in the stage of diffuse hypertrophy.
2. Iodine deficiency goitre
   • Daily iodine requirement is about 100–125 micrograms.
   • Common in hill/mountain areas and low-lying areas because of decreased iodide content of water.
   • This causes iodine deficiency goitre, by the same feedback mechanism.
   • This is treated by iodised salt which is used for food and also iodine-containing preparations.
   • If the iodine deficiency status continues for a long time it results in the accumulation of colloid material in the gland and causes colloid goitre.
   • All these 3 types of goitre if left untreated will change to multinodular goitre.
3. Goitrogens such as cabbage, and drugs such as PAS and sulfonamides, cause goitre by
   preventing the oxidation of iodide to iodine.

• Stage 1: Stage of diffuse hypertrophy and hyperplasia of the thyroid.
• Stage 2: Due to fluctuating levels of TSH because of pregnancy, lactation, menstruation, etc. Some areas in the thyroid are overstimulated and are converted to active follicles.
• Stage 3: The active follicle ultimately undergoes necrosis and many such necrosed follicles join to form a nodule. Many such nodules form a multinodular goitre. Nodules contain necrosed tissue, i.e. inactive tissue. The internodular tissue is active.

Multinodular Goitre Clinical features

• Multinodular goitre is common in females. Female: male ratio is 10:1. Seen in the age group of 20–40 years.
• Long-duration swelling in front of the neck, dyspnoea due to tracheomalacia and dysphagia are the presenting features.
• The gland is nodular, and firm in consistency and both the lobes are enlarged. Sometimes, only one nodule may be found clinically other nodules may be in the process of developing.

• Hard areas may suggest calcification and soft areas, necrosis.
• The sudden increase in size with pain is mainly due to a haemorrhage in a nodule.

The most common site of a nodule is at the junction of the isthmus with one lobe.

Complications of multinodular goitre

1. Calcification in long-standing MNG.
2. Sudden haemorrhage in one of the nodules causes sudden enlargement of the gland and even causes dyspnoea.
3. In 10–20% of cases, patients can develop secondary thyrotoxicosis with CVS involvement.
4. Toxic multinodular goitre is also called Plummer’s disease.
5. In 8–10% of cases, MNG can change into a follicular carcinoma of the thyroid, and at times papillary carcinoma.

Management Of Multinodular Goitre

Multinodular Goitre Investigations

1. Complete blood picture (CBP), routine urine examination and fasting and postprandial blood sugar to rule out diabetes mellitus.

2. X-ray of the neck: Anteroposterior and lateral view.

• To see compression of the trachea to check the feasibility of intubation during anaesthesia.
• To rule out retrosternal extension-soft tissue shadow was seen.
• Calcification in long-standing MNG

3. Indirect laryngoscopy¹ is done to see vocal cord mobility.

4. Isotope scan by using a tracer dose of radio-iodine.

It can demonstrate 3 different patterns as follows:

1. Hot nodule: The gland does not take up isotope but the nodule takes it up, which is a feature of autonomous solitary toxic nodule. Here, the normal thyroid tissue is suppressed.
2. Warm nodule: Entire gland takes up isotope. This is typical of Graves’ disease (primary thyrotoxicosis) wherein each cell is active and equally stimulated.
3. The cold nodule is a nodule which does not take up an isotope. It should be remembered that only 10% of the cold nodules are malignant.
   • Keeping this in mind, many surgeons do not investigate MNG with isotope scans. The assessment of malignancy is done clinically and when in doubt, a frozen section at the time of surgery is done

Cold Nodule—Differential Diagnosis

1. Haemorrhage
2. Carcinoma
3. Thyroiditis
4. Thyroid cyst

In non-toxic MNG, a routine radio-iodine scan is not done unless there is a strong suspicion of malignancy.

5. Ultrasonography: High-frequency ultrasound is very useful for investigation, especially in cases of solitary nodules.

Even in multinodular goitres, ultrasound-guided FNAC can be done. It can also detect clinically impalpable lymph nodes in the neck.

6. Fine needle aspiration cytology (FNAC) should be done in all cases of multinodular goitre even when an isotope scan is not done because it is a simple and useful investigation which can detect malignancy. Also, some cases turn out to be Hashimoto’s thyroiditis which can be managed with hormones, thus avoiding surgery.

Prevention

Prevention can be tried in the early stages.

Prevention Of MNG

• Puberty goitre: 0.1 to 0.2 mg of thyroxine
• Iodine deficiency goitre: Use iodised salt, seafood, milk, egg, etc.
• Goitrogens: Avoid cabbage, drugs

Classification Of Investigations—Goitre

1. Simple goitres
   • Routine—Blood and urine tests, chest X-ray
   • Indirect laryngoscopy
2. Toxic goitres
   • Routine
   • T₃, T₄, TSH
   • Isotope scan
3. Malignant goitre
   • Routine
   • Isotope scan, bone scan
   • FNAC

Goitre Surgery

• Total or near-total thyroidectomy is being favoured nowadays because of the following reasons:

1. The frozen section is not reliable. Hence, even if malignancy is detected, re-exploration which has increased chances of nerve injury can be avoided.
2. Recurrence of MNG can be avoided.
3. Thyroid hormone replacement is mandatory. May require calcium supplements of
   Parathyroids are also removed.

• Subtotal thyroidectomy: In this operation, parts of the right and left lobes and the entire isthmus are removed flush with the tracheal surface leaving behind a little tissue in the tracheoesophageal groove to protect recurrent laryngeal nerve and parathyroid gland. This avoids RLN paralysis and hypothyroidism.

• Some surgeons treat these patients prophylactically with 0.2 mg of thyroxine to suppress the TSH stimulation in the postoperative period, for a period of 2–5 years.

Retrosternal Goitre

• Very often, it is a multinodular goitre which develops in the neck and is slowly pulled down behind the sternum due to the following reasons:

1. Negative intrathoracic pressure
2. Pretracheal muscles are strong in men
3. Short neck, obesity

• Rarely, it arises from an ectopic thyroid tissue.

Retrosternal Goitre Clinical Types

1. Substernal: The most common type where the lower border of the gland is behind the sternum.
2. Intrathoracic: No thyroid is seen in the neck, diagnosed by radio-iodine scan.
3. Plunging goitre: When a patient is asked to cough, intrathoracic pressure increases. As the thyroid plunges out, the lower border of the gland is clearly seen in the neck.

Clinical Features of Retrosternal Goitre

• It can be suspected when the lower border of the swelling is not seen.
• Most of the patients have difficulty in breathing or even stridor.
• Dysphagia is more common
• Engorgement of neck veins and superficial veins. These become more prominent when the hands are raised above the head, and the arms touch the ears—“Pemberton’s sign”.

Retrosternal Goitre Investigations

They are similar to MNG. However, an isotope scan is very useful in the diagnosis of intrathoracic goitres.

Investigations Treatment

• It can be easily explored through the neck incision and removed.
• Very, very rarely, the sternal split may be necessary.

Retrosternal Goitre

• Very often it is an MNG with a lower border unseen
• Rarely from ectopic thyroid tissue
• Severe breathlessness even though small
• Drugs should not be given if it is toxic
• Pressure effects diagnosed by Pemberton’s test
• Surgical excision is the treatment

Toxic Goitre—Thyrotoxicosis

• It is a complex disorder which occurs due to increased levels of thyroid hormones (hyperthyroidism) and manifests clinically with various signs and symptoms involving many body systems. The following are the causes of thyrotoxicosis.

1. Primary thyrotoxicosis (Graves’ disease, exophthalmic goitre).
2. Secondary thyrotoxicosis: Secondary to multinodular goitre.
3. Solitary toxic nodule: Autonomous nodule which is not under the influence of TSH, but occurs due to hypertrophy and hyperplasia of the gland (tertiary thyrotoxicosis).
4. Other causes of thyrotoxicosis
   • Thyrotoxicosis factitia: False thyrotoxicosis occurs due to overdosage of thyroxine, given for puberty goitre.
   • Jod-Basedow’s thyrotoxicosis: Jod means iodine in the German language, and Basedow means toxic goitre. Iodine-induced thyrotoxicosis (iodine given for hyperplastic endemic goitres)
   • The initial stage of thyroiditis
   • Very rarely, malignant goitres can be toxic (differentiated carcinoma).
   • Neonatal thyrotoxicosis occurs in babies born to thyrotoxic mothers.
   • TSH-secreting tumours of the pituitary
   • Struma ovarii
   • Drugs: Amiodarone is given as an antiarrhythmic drug. In the clinical examination, primary thyrotoxicosis and secondary thyrotoxicosis are commonly kept as long cases.