Endocrine Flashcards
Development of upper parathyroid glands
Arise from fourth branchial arch
Usually found at the back of the thyroid above the inferior thyroid artery
Development of the lower parathyroid glands
Arise from the third branchial arch
Usually in association with thyrmus
Level of the thyroid glands
Lie on front of trachea and larynx at C5-C7
Superior thyroid artery
Branch of external carotid artery
Inferior thyroid artery
Branch of thyrocervical trunk of subclavian artery
As the inferior thyroid artery appraoches the galdn it normally passes in front of the recurremt laryngeal nerve
Lymphatic drainage of the thyroid
Pretracheal and mediastinal nodes
Veins of the thyroid
Superior
Middle
Inferior
.. thyroid veins
All drain into the internal jugular and innominate veins
Innervation of the intrinsice muscles of the larynx
Recurrent laryngeal nerve supplies all of them except Cricothyroid
Innervation of the cricothyroid muscles
External branch of the superior laryngeal nerve
Innervation providing sensation above the vocal cords
Internal branch of the superior laryngeal nerve
Innervation providing sensation below the vocal cords
Recurrent laryngeal nerve
Non-toxic multinodular goitre
Multiple nodules
Caused by iodine deficiency
If biochemistry normal, no need for radio-isotype uptak e scan
Mx: Thyroidectomy and replacement
Can become toxic: a long-standing non-toxic goitre develops hyperactive nodule(s) that function independently of TSH levels
Management of hashimoto’s
Replacenebt thyroxine
Thyroidectomy seldom needed and carries higher riusk of recurrently laryngeal nerve injury due to firmness of gland
Firm painless swelling and tracheal compression
Riedel’s thyroiditis
Mx: Aspirated cysts that do not re-fill with negative cytology
OP follow-up
Residual aspirate or blood-stained aspirare
Suspect Papilllary carcinoma
FNAC cannot distinguish bewteen…
cytopathologist cannot distinguish between a follicular adenoma and follicular carcinoma
Histopath needed
Primary thyrotoxicosis
Grave’s Disease
Toxic multi-nodular goitre
Toxic Adenoma
Management of primary thyrotoxicosis
Block and replace
Carbimazole (15mg QDS) and Thyroxine
Radio-iodine
Surgery
- Carbomazole used pre-op to render euthyroid
- B-blockers used pre-op to decrease vascularity
- B-blockers continued 7 days post op to avoid effects of thyroid storm
Most common thyroid cancer
Papillary carcinoma (50%)
Papillary carcinoma
Most prevalent before the age of 40
Slow-growing solitary growth
Lymphadenipathy palpable in 1/3
Complex papillary folds lined by several layers of cuboidal cells project into cystic space
Mx:
Thyroxine replacement to supress TSH
Commonly multifocal, so bilateral total lobectomy
Microscopic disease (< 1cm and unifocal) and tumours with favourable histology and < 2cm in size may be treated by single lobectomy
Radio-isotype scan post-op to detect possible mets
10-year survival rates approaching
90%
Follicular carcinoma
30% of thyroid carcinomas
Commonest age 30-50 yrs
Presents as a solitary thyoid mass
Haematogenou spread common, lymph node spread rare
Malignant cells are arrange dinto solid mass with rudimentary acini
Mx:
Total thyroidectomy with sparing of parathyroids
Post-op radio-isotype scan, use radio-ionide to treat mets
Replace with T3 and then T4 to supress TSH
Thyroglobulin should be undetectable - if found indicates recurrence
10-year survival rate is 75%.
Anaplastic carcinoma
Elderly women
Highly malignant
Peri-neural invasion –> recurrently laryngeal and cervical sympathetic (horners)
Pulmonary metastasis common
Mx
Surgery rarely appropriate, but can used to relieve tracheal compresison
External bean radiotherapy
Medullary carcinoma
Parafollicular C Cells - Raised Calcitonin
MEN II (Sipple’s Syndrome)
Hard enlargement of one or both thyroid glands
50% have cervical lymph node invasion
Pre-Op CT screening for phaeochromocytoma
Ret - proto oncogene
Mx
Total thyroidectomy and, if the calcitonin
level is raised, dissection of the lymph nodes in the
central compartment of the neck (levels 6 and 7).
Structures divided durng thyroidectomy
Travserse skin incision 2cm above sternal notch
Longitudinal division of fascia
Separation of strap muscles
Each lobe is mobilized by dividing the vessels supplying the superior pole, the middle and inferior thyroid veins, and the inferior thyroid artery
Damage to the external branch of the superior laryngeal nerve
Damaged whilst securng superior thyroid pedicle
- -> inability to tense vocal cords: weaker voice with ptich-range change
- -> lack of sensation to mucous membrane of upper larynx: allows foreign bodies to enter larynx more readily
Damage to the recurrent laryngeal nerve
Division –> paralsysis of vocal cords in cadaveric position
Normal cord on the other side compensates by crossing the midline in phonation, but the voice is altered in timbre, hoarse, weak and breathy
Some degree of stridor
Bilateral recurrent laryngeal nerve injury
Bilateral nerve injury results in stridor and ineffective
coughing when the endotracheal tube is withdrawn at theend of the operation
The tube is reinserted immediately and, if there is no early improvement, tracheostomy may be required. The paralysis is originally flaccid, but fibrosis draws the cords together and, even if tracheostomy has been
avoided, increasing dyspnoea on exertion may be troublesome.
Blood supply to the parathyroids
Inferior thyroid artery
Development of anterior pituitary
The anterior pituitary develops from an epithelial outgrowth from the pharynx (Rathke’s pouch).
Complications of transcranial approach to hypophysectomy
Anosmia
Diabetes insipidus
Development of adrenal cortex
Mesoderm
Development of adrenal medulla
Chromaffin ectodermal cells of the neural crest
Adrenal phaeochromocytomas
Secrete noradrenaline and adrenaline
Extra-adrenal phaeochromocytomas
Secrete noradrenaline only
Adrenal ‘incidentaloma’
If non-functioning and <3.5 cm in diameter, further
investigation and exploration are unwarranted
Indications for adrenalectomy
Cushing’s syndrome caused by adrenal tumours
Cushing’s disease not controlled by pituitary surgery
Conn’s syndrome caused by adrenal tumour
Phaeochromocytoma
APUD Cells
Have capacity to store and synthesise amines: ATCH, catecholamines, calcitonin, secretin, gastrin, cholecystokin, enteroglucagon, somatostatin, VIP
Found in:
- anterior pituitary
- adrenal medulla
- thyroid gland
- intestine
MEN I
Hyperplasia or adenaomas of the:
- Pancreatic islets
- Parathyroid
- Anterior pituitary
There may also be non-functioning tumours of the thyroid, pituitary, adrenal cortex and soft tissues (lipomas), and functioning carcinoid tumours of the gut or lungs.
Mutations in the MENIN gene on chromosome 11
MEN II
Medullary carcinoma of the thyroid
Phaeochromocytoma
Parathyroid hyperplasia
Ret proto-oncogene chromosome 10
Urinary 5-hydroxyindolaecatic acid
Carcinoid disease
Carcinoid syndrome
Periodic flushing Diarrhoea Bronchoconstriction Wheezing Red-purple discoloration of the face
Right-sided heart disease, notably pulmonary stenosis -> death
