Section 7

TFT results: 

  • TSH: 5.8 mU/L (0.27 – 4.2 mU/)L
  • Free T4: 10   (12 – 22 pmol/L)
  • Thyroid peroxidase antibody >1000IU/ml

Interpret the blood results above. What is the likely diagnosis?

  • Raised TSH, low T4 in keeping with hypothyroidism
  • Likely due to Hashimoto’s disease due to raised TPO Antibodies

What investigations might you order?

May order ultrasound neck if evidence of nodules

What is the long term treatment?

Thyroxine replacement

List two indications for surgery

  • Further investigation or management of thyroid nodule
  • Large goitre causing compressive symptoms or cosmetic concern

Supporting Documents

2015: Management of primary hypothyroidism: statement by the British Thyroid Association Executive Committee  https://www.british-thyroid-association.org/sandbox/bta2016/bta_statement_on_the_management_of_primary_hypothyroidism.pdf

2014: The British Thyroid Association Guidelines for the Management of Thyroid Cancer . https://onlinelibrary.wiley.com/doi/pdf/10.1111/cen.12515

Thyroid gland

Surrounded by its own capsule + pretracheal fascia. 2 lobes + isthmus each having a lateral, medial and posterior surface.

  • Lateral surface– sternothyroid, SCM and sternohyoid
  • Medial surface– external laryngeal nerve, RLN, larynx, pharynx, oesophagus and trachea.
  • Posterior surface– PT glands, carotid sheath, inferior thyroid artery, thoracic duct on left.

Blood supply-

  • Arterial
    • Superior thyroid artery from external carotid,
    • Inferior artery from thyrocervical trunk,
    • Thyroid IMA from arch of the aorta.
  • Venous
    • Superior thyroid vein to internal jugular or facial vein,
    • Middle thyroid vein into internal jugular vein,
    • Inferior thyroid vein via a plexus into the brachiocephalic vein.

Lymphatic– lower pole to postero-inferior deep nodes, upper to antero-superior deep nodes.

Embryology

  1. First appears at foramen caecum in the floor of pharynx
  2. Descends to reach final position by 7th week
  3. It is connected by thyroglossal duct and so the cysts here along the path of descent and move up on tongue movement
  4. Ectopic tissue can be seen in the tongue, hyoid bone, deep to SCM and superior mediastinum

Thyroid physiology– produces 3 hormones, iodine is needed and is absorbed from plasma I- and converted to iodine (I2) by thyroid peroxidase in the follicular cells:

  1. Thyroxine T4
  2. Triiodothyronine T3
  3. Calcitonin

T3 and T4 circulate bound to:

  1. Thyroxine binding globulin
  2. Thyroxine binding prealbumin
  3. Albumin.

T3 is more potent than T4, therefore T4 is converted by de-iodination. The thyroxine goes into the cell and binds in the nucleus causing increasing mRNA expression and upregulation of certain genes.

Thyroxine functions– stimulates oxygen consumption in cells of the body and increases B receptor sensitivity to catecholamines:

  • increased protein catabolism
  • increased temperature
  • increased fat mobilisation and degradation
  • increased gluconeogenesis, glycogenolysis, and glucose absorption from the gut
  • CNS development
  • regulation of gut development as well as hair and skin.

Thyroid regulatory problems:

Causes

Features

Treatment

Hyperthyroidism

(thyrotoxicosis)

Graves

Toxic nodule

Toxic multinodular goitre

Thyroxine overdose

Thyroid carcinoma

Iodine therapy

Hyperfunctioning ovarian teratoma

Heat intolerance

Low blood cholesterol

Anxiety/irritability

Diarrhoea

Weight loss/muscle wasting

Tremor

Tachycardia

Arrhythmia

Menstrual irregularities

Lid lag/retraction

Pretibial myxoedema

Thyroid acropachy

Palmar erythema

Medical- carbimazole

Radioactive iodine

Surgical

Hypothyroidism

Autoimmune thyroiditis (haschimotos and atrophic thyroiditis)

Iodine deficiency

Post-irradiation

Tumour infiltration

Antithyroid drugs

Hypopituitarism

Cold intolerance

Increased cholesterol

Sluggish mental state

Menstrual irregularities

Weight gain

Fatigue

Bradycardia

Cretinism if prenatally

Thyroxine

Thyroid swelling– many causes:

  • Solitary nodule- multinodular goitre, adenoma, carcinoma, haemorrhage into cyst (chocolate cyst)
  • Diffuse swelling– multinodular goitre, hashimoto’s thyroiditis/ grave disease, cancer. 

Investigate– FNA, TFTs, USS, thyroid autoantibodies

Hashimoto’s– low thyroid- autoimmune with cell and AB mediated reaction.

  • Symptoms– low mood, weight gain, hair loss, tiredness, psychosis, cold/hot intolerance, mania, high cholesterol, hypoglycaemia, constipation, muscle weakness, migraine, memory loss, infertility, cramps.
  • TPO very high >1000, if caught early then elevated thyroglobulin
  • Other tests– TSH, T3/4, anti thyroglobulin (anti-Tg) antibodies, anti TPO and anti-microsomal antibodies
  • Examination– firm non tender goitre
  • May require thyroidectomy as thyroid gland changes to lymphoid tissue which can turn into lymphoma

Goitre in general:

  • Causes– puberty, pregnancy, graves, hashimotos, thyroiditis (subacute, granulomatous, De Quervians, silent, Riedels, acute infective. Sarcoidosis, TB, Iodine deficiency, idiopathic
  • Symptoms:
    • Compression- dyspnoea, dysphagia, neck lump, weak voice
    • Hyperthyroidism
    • Hypothyroidism
  • Treatment- thyroidectomy if dyspnoeic, dysphagic or hyperthyroid (Graves).

De- quervians– post URTI, tender thyroid gland.

Thyroid cancer

  1. Benign– adenoma- common, can be multiple- full of colloid, can cause hyperthyroidism.
  2. Malignant (most to least common)
    1. Papillary– 70%- young patients, hx neck radiation. Often multifocal with lymph node metastasis.
      1. Histology- orphan annie nuclei (pale and empty looking)
      2. Most are TSH dependant
      3. 90% 10 yr survival
      4. Treat with total or hemithyroidectomy
    2. Follicular–  20%- malignant glandular unifocal lesion- distant metastasis and cervical lymph nodes.
      1. Treated with total thyroidectomy
    3. Medullary– 5%- C-cell tumour (calcitonin)- Familial, screen for MEN syndrome. Multifocal and spread distant mets via blood and lymph nodes. Treatment total thyroid
    4. Anaplastic– <5% tumours- old patients, worst prognosis. Rapidly mets to lymph nodes but locally invasive. 5-yr survival poor. Treatment is mostly debulking.

Thyroidectomy– indications- overactivity, cosmesis, compression, carcinoma. Pre-op patients need to be euthyroid otherwise thyroid crisis may ensue intra-operatively (carbimazole). 

Procedure:

  1. Extended neck
  2. Horizontal incision, 2cm over manubrium
  3. Skin, subcutaneous fat
  4. Subplatysmal flaps raised
  5. Vertical incision into investing fascia and connective tissue made, straps retracted laterally.
  6. Straps may need to be divided
  7. Superior thyroid artery tied- close to gland (avoid SLN damage)
  8. Inferior thyroid artery tied- away from gland (avoid RLN damage) can be tied in-continuity to avoid RLN damage.
  9. Thyroid desiccated fully if not subtotal where you can leave a lateral slither.
  10. Isthmus taken off trachea- oversewn if hemithyroidectomy
  11. Closure in layers- straps not closed
  12. Suction drain and clips to skin

Complications– bleeding, airway compromise, SLN/RLN damage, hypocalcaemia (temporary or permanent)

  • Joll’s triangle– midline, superior thyroid pedicle and straps- superior laryngeal nerve
  • Beahr’s triangle– common carotid, trachea and inferior thyroid artery- RLN

Hypocalcemia– perioral numbness, muscle cramps, carpopedal spasm, wheezing from bronchospasm, voice changes, fatigue, seizures.

Treat with 10mls 10% calcium gluconate IV slow bolus. Then 40 in 24 hrs. Can give sando cal.

Ergocalciferol- vit D replacement.

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