General Surgery
Thyroid and Parathyroid
MBBS surgery notes on thyroid and parathyroid: goitre, thyroid cancers, recurrent laryngeal nerve and hyperparathyroidism, mapped to NMC codes SU22.1 to SU22.6.
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Thyroid and Parathyroid
MBBS surgery notes on thyroid and parathyroid: goitre, thyroid cancers, recurrent laryngeal nerve and hyperparathyroidism, mapped to NMC codes SU22.1 to SU22.6.
This chapter covers the surgical diseases of the thyroid and parathyroid glands. It spans goitre, thyroid cancers, the nerves at risk in surgery, postoperative hypocalcaemia and primary hyperparathyroidism.
High-yield: Thyroid and Parathyroid
- A goitre is an enlarged thyroid and may be diffuse, multinodular or solitary nodular, and toxic or non-toxic.
- A thyroid swelling moves up with swallowing because the gland is bound to the larynx by the pretracheal fascia.
- A thyroglossal cyst moves up on protrusion of the tongue because of its attachment to the hyoid and foramen caecum.
- Fine needle aspiration cytology is the key investigation to assess a thyroid nodule for malignancy.
- Papillary carcinoma is the commonest thyroid cancer, spreads to lymph nodes and has an excellent prognosis.
- Follicular carcinoma spreads by the bloodstream to lung and bone and cannot be diagnosed on cytology alone because capsular invasion must be seen.
- Medullary carcinoma arises from parafollicular C cells, secretes calcitonin and can be part of multiple endocrine neoplasia type 2.
- Anaplastic carcinoma is aggressive, occurs in the elderly and has a very poor prognosis.
- The recurrent laryngeal nerve is at risk in thyroid surgery; unilateral injury causes hoarseness and bilateral injury can cause airway obstruction.
- The external branch of the superior laryngeal nerve supplies cricothyroid and its injury weakens the high-pitched voice.
- Hypocalcaemia after total thyroidectomy results from inadvertent removal or devascularisation of the parathyroid glands.
- Primary hyperparathyroidism is usually due to a single parathyroid adenoma and causes hypercalcaemia.
- The features of hypercalcaemia are recalled as stones, bones, abdominal groans and psychic moans.
- Thyroid storm is a life-threatening exacerbation of thyrotoxicosis that can be precipitated by surgery on an unprepared toxic patient.
- A toxic patient is rendered euthyroid before surgery with antithyroid drugs, and Lugol iodine is given to reduce gland vascularity.
Thyroid cancers at a glance
- **Papillary:** Commonest; lymphatic spread; excellent prognosis; often in younger patients.
- **Follicular:** Haematogenous spread to lung and bone; needs histology, not just cytology, for diagnosis.
- **Medullary:** From C cells; secretes calcitonin; may be part of multiple endocrine neoplasia type 2.
- **Anaplastic:** Elderly; aggressive; very poor prognosis.
NMC competencies in this chapter
- **SU22.1:** Anatomy, goitre and assessment of thyroid swellings
- **SU22.2:** Thyroid neoplasms and their management
- **SU22.3:** Thyrotoxicosis and preoperative preparation
- **SU22.4:** Thyroid surgery and its complications
- **SU22.5:** Parathyroid disorders and hyperparathyroidism
- **SU22.6:** Postoperative hypocalcaemia and its management
Frequently Asked Questions
Why does a thyroid swelling move on swallowing?
The thyroid is bound to the larynx and trachea by the pretracheal fascia, so it moves up with the larynx during swallowing, unlike most other neck lumps.
What is the commonest thyroid cancer?
Papillary carcinoma. It spreads through the lymphatics, is often multifocal and has an excellent prognosis, especially in younger patients.
Why does hoarseness follow thyroid surgery?
The recurrent laryngeal nerve runs close to the gland and can be injured, causing vocal cord paralysis and hoarseness; bilateral injury can obstruct the airway.
Why does hypocalcaemia occur after total thyroidectomy?
The parathyroid glands can be inadvertently removed or lose their blood supply during surgery, reducing parathyroid hormone and causing a fall in serum calcium.
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