Thyroid & Neck Flashcards
Describe the boundaries of the posterior cervical triangle.
The posterior cervical triangle is bounded by:
• the posterior border of sternocleidomastoid muscle;
• the anterior border of the trapezius muscle;
• the middle third of the clavicle, forming the base of the triangle;
• the roof, formed by cervical fascia; and
• the floor, formed by muscles and deep cervical fascia.
• The posterior triangle can then be subdivided into the occipital triangle and the supraclavicular or subclavian triangle. The posterior triangle contains mostly vessels and nerves that connect the neckand the upper limb. It also contains superficial and deep lymph nodes.
Describe the boundaries of the anterior cervical triangle.
- the anterior median line of the neck;
- the inferior border of the mandible;
- the anterior border of sternocleidomastoid muscle;
- the roof of platysma muscle and subcutaneous tissues;
- the floor, formed by the pharynx, larynx and thyroid gland;
- the apex which is the jugular notch; and
- the base, which is a line from the inferior border of the mandible to the mastoid process.
- The anterior triangle can then be further subdivided using the digastric, stylohyoid and omohyoid muscles. Superior to the hyoid, the submental and submandibular triangles are formed. Inferior to the mandible, the carotid and muscular triangles are formed.
- The anterior triangle contains glandular structures (such as the thyroid and parathyroid glands) and lymphatics. The carotid triangle in particular contains the carotid vessels and associated veins and nerves.
What laboratory tests would be performed if the parathyroid was the main concern?
Alkaline phosphatase
□ Elevated in hyperparathyroidism sometimes
Calcium
□ Serum calcium and phosphorus levels are reflective of parathyroid function
□ Elevated in hyperparathyroidism, malignant tumours, hyperthyroidism, excessive calcium intake, parathyroid adenoma
□ Decreased in massive blood transfusion
□ Vit d deficiency
□ Hypoparathyroidism
□ Acute pancreatitis
Parathyroid hormone
□ Secreted by parathyroid glands
□ Normal is between 1 and 6.5pmol/L
□ Elevated in hyperparathyroidism
Decrease hypoparathyroidism, hypocalcemia due to malignant disease
Describe radioactive thyroid uptake.
Radioactive iodine uptake
□ Normal is 5-30% of administered dose
□ Elevated in graves disease, toxic MNG, hypopituitary disease, hyperthyroidism (not always)
Decreased in subacute thyroiditis, hypothyroidism, thyrotoxicosis, metastatic thyroid carcinoma, struma ovarii
Describe TSH test.
TSH levels
□ TSH is secreted by anterior pituitary on stimulation by TRH from hypothalamus
□ Stimulates release of T3 and 4
□ Normal 0.4-6.3mU/L
□ Elevated in hypothyroidism and thyroiditis due to poor response from thyroid tissue to secrete T3 and 4 so further TSH is release
□ Decreased in hyperthyroidism and thyroid cancer due to increased circulation of T3 and 4 reducing TSH
Describe T3 and T4 tests.
T4- secreted in response to TSH, small amount circulates freely
□ Normal 12-26pmol/L
□ Elevated in hyperthyroidism
□ Decreased in hypothyroidism
T3- more potent and is secreted in response to TSH
□ Normal 3.3-7.5pmol/L
□Elevated in hyperthyroidism
Case 1: Clinical features:
Feeling hot, increased sweating, weight loss, enlargement of the thyroid gland, rapid heart rate and palpitations, anxiety and restless hyperactivity.
A patient with the described clinical features is presenting with common features of Graves’ disease with hyperthyroidism. Laboratory tests would be performed to identify TSH levels, T3 and T4. T3 and T4 will be elevated above normal ranges. TSH will be decreased due the feedback mechanism not requiring further TSH secretion in the presence of increased T3 and T4 circulating in the blood. RAIU could be also performed, but the other tests are more specific as hyperthyroidism does not always cause high iodine uptake.
Graves’ disease is the most common diffuse abnormality of the thyroid gland. It is an auto-immune disorder in which antibodies are produced against TSH receptors. These are called thyroid-stimulating antibodies which bind to TSH receptors and stimulate thyroid hormone secretion (other terms for this antibody you may come across are long-acting thyroid stimulator or thyroid-stimulating immunoglobulins).
Graves’ disease generally occurs in younger women, and may cause exophthalmos (protruding eyeballs), smoothly enlarged thyroid, increased appetite, weight loss, muscle wasting, diarrhoea, increased nervousness and excitability, raised blood pressure, warmth, sweatiness and amenorrhoea.
Case 2:Clinical features:
Cold intolerance, facial and extremity oedema, lethargy, weight gain, bradycardia, constipation, hair loss.
A patient with the described clinical features is presenting with common features of hypothyroidism. Laboratory tests would be performed to identify TSH levels, T4 and T3. TSH will be elevated above the normal range as it is further secreted due to low circulating levels of T3 and T4. This is a sensitive early marker. A RAIU test could be also performed and would show reduced iodine uptake.
Hashimoto’s thyroiditis is the most common cause, clinically presenting with reduced thyroid function and the symptoms of myxedema due to reduced metabolic rate. This is an auto-immune disease that presents more often in women than men. Occasionally the initial tests in Hashimoto’s thyroiditis may show hyperthyroid levels, but usually the patient does not present until the disease has passed through the euthyroid state into an increasing hypothyroid state.
Symptoms of this disease are as described in the case history; the thyroid gland is usually prominent and ‘rubbery’ to palpate. TSH tests can be further used to monitor the effectiveness of the thyroid hormone replacement therapy used to treat the disease. Other causes of these symptoms may be previous thyroidectomy or low iodine intake.
Case 3
Clinical features:
Prominent, irregular neck swelling, difficulty in swallowing, occasional neck pain.
A patient with the described clinical features is presenting with common features of multi-nodular goitre. Laboratory tests would be performed to identify RAIU, TSH levels, T3 and T4. These may all show normal levels, unless there is a dominant functional adenoma that will cause an elevation of the RAIU, T3 and T4 tests, with a reduction in the TSH levels. Usually these goitres are euthyroid in nature.
Multinodular goitre may present as a generalised enlargement of the thyroid gland or it may have irregular margins with variable sized, palpable nodules. Often one nodule may rapidly increase in size due to internal haemorrhage into the nodule. This can cause pain and increase the patient’s symptoms of dysphagia.
Case 4: Clinical features:
History of renal calculi, unilateral (mild) neck swelling.
A patient with the described clinical features is presenting with common features of parathyroid adenoma. Laboratory tests that would be performed will assess serum calcium and parathormone levels. Both of these will be elevated. This effectively rules out a malignant cause of the palpable mass as you would expect the parathormone levels to be suppressed with malignancy.
Parathyroid adenomas are often small, but may enlarge to be palpable. Careful assessment to look for additional enlarged glands is important, so as to rule out parathyroid hyperplasia.
Briefly describe the embryological development. of the thyroid.
The thyroid gland is the first endocrine gland to form in the embryo. It appears during the fourth embryonic week as a median endodermal thickening in the floor of the primitive pharynx which forms a downgrowth known as the Thyroid Diverticulum. The developing thyroid descends through the tissues of the neck at the end of a slender thyroglossal duct, which breaks down by the end of the fifth embryonic week. The isolated thyroid gland continues to descend, reaching its final resting place just inferior to the cricoid cartilage by the seventh week. The only remnant, normally, of the thyroglossal duct is the foramen caecum of the tongue.
During the course of the scan, a patient who has until now been accepting of the procedure, refuses to continue with the scan any longer. List reasons why this patient may have withdrawn consent.
Environmental factors:
• the room may be too hot, too cold, too noisy, too smelly.
• the bed or scanning position may be too uncomfortable to tolerate further.
Sonographer factors:
• you may not have explained the procedure fully to the patient and are doing something they did not expect.
• you may be communicating poorly with the patient, ignoring them, being rude or not explaining what you are doing.
• Pressing too hard on their neck while scanning, causing pain or difficulty in swallowing or breathing.
• Leaning on the patient’s chest/breasts, even if inadvertantly.
Department factors:
• Rudeness of staff, whether real or perceived; this may include the receptionist, nurse/aid, sonographer or sonologist.
• Continual interruption in the ultrasound room by other staff members or phone calls.
• Excessive waiting while checking the films or seeking the sonologist.
Patient/disease process factors:
• Some patients with abnormally functioning thyroid glands may experience episodes of paranoia and/or depression. They may be very sensitive to anything you may say to them.
• The neck or mass may be very tender, especially when being scanned.
• The patient may be afraid of what the abnormality may be; e.g. cancer. This may be exacerbated if there is a relevant family history or if they are present due to a recurrence of a previous problem.
Discuss the advantages of an FNA
Advantages: • minimal materials (usually a very simply procedure) • inexpensive • quickly performed • local anaesthetic often not used • minimal discomfort (usually) • small bruise only (usually)
Discuss the disadvantages of an FNA.
Disadvantages:
• sample may be inadequate ( reduced if pathologist is present to check sample )
• false positive/false negative/equivocal aspirates
• dependence of cytopathology expertise
• specific tissue-related potential pitfalls.
Discuss the advantages of a core biopsy
Advantages: • inexpensive • relatively atraumatic • may obviate the need for open biopsy • higher diagnostic yield (though there is some varying opinion about this)
