Endocrine

Question 1

what is a phaeochromocytoma?

Answer 1

A tumour arising from catecholamine-producing chromaffin cells of the adrenal medulla that classically presents with headaches, diaphoresis, and palpitations in the setting of paroxysmal hypertension

Question 2

what are the S&S of phaeochromocytoma?

Answer 2

• headaches
• palpitations
• diaphoresis
• paroxysmal HTN
• episodic pallor
• Impaired glucose tolerance (catecholamines increases glycogenolysis and inhibits insulin)
• panic attacks or sense of doom

Question 3

what are the investigations for phaeochromocytoma?

Answer 3

• 24h urine collection and assessment for vanillylmandelic acid (VMA) and noradrenaline is most accurate for diagnosis (97% sensitive).
• Clonidine suppression test (failure of urine levels to fall after clonidine dose) confirms the diagnosis where urine levels are borderline.

Localizing studies
• Thoraco-abdominal CT or MRI scanning. First-line test, especially for adrenal and sympathetic chain tumours.
• MIBG (meta-iodo-benzyl-guanidine) scanning localizes extra-adrenal sites not seen on CT or MRI

Question 4

what is MEN1 ?

Answer 4

A syndrome of the ‘3Ps’.

• Parathyroid gland tumours. By age 40, 95% of patients have hypercalcaemia which is the commonest manifestation.
• Pancreatic islet cell tumours. Prevalence of 30–75%. Usually multicentric, slow growing. Secrete multiple polypeptides (insulin and gastrin commonest). Gastrinoma leads to Zollinger–Ellison syndrome (recurrent and multiple peptic ulcers, severe reflux oesophagitis, and diarrhoea). Rarer tumours are VIPoma, glucagonoma, somatostatinoma.
• Anterior pituitary tumours. Detected in 15–40%. Commonest is prolactinoma. Rarer are GH- (causes acromegaly) or ACTH- (causes Cushing’s disease) secreting tumours.

Question 5

how is MEN1 investigated?

Answer 5

• Biochemical screening from second decade in known families (serum calcium, PTH, prolactin, and insulin growth factor-1 (IGF-1) for pituitary lesions, and serum glucose, insulin, gastrin, and chromogranin for pancreatic tumours).
• Genetic screening can be used for offspring of known index cases. Because 10% of menin mutations are de novo, siblings of an index case are not necessarily at risk.

Question 6

what is MEN2A?

Answer 6

Medullary thyroid carcinoma (MTC).

• Originates in the calcitonin-secreting parafollicullar C-cells (derivatives of the neuroectodermal tube);
• Commonly multicentric and bilateral and appear on a background of C-cell hyperplasia;
• Presents as unilateral or bilateral thyroid nodules with/without associated cervical lymphadenopathy;
• Associated secretion of other (some unidentified) peptides can lead to severe diarrhoea.

Phaeochromocytoma (in 50% of patients).

Primary hyperparathyroidism (15% of patients).

Question 7

what is MEN2B?

Answer 7

MTC.
Phaeochromocytoma.
‘Marfanoid-specific body habitus’ (tall, slender, high arched palate, and long extremities), 90% of patients.

MEN-2B is associated with mucosal neuromas and intestinal ganglioneuromatosis and characteristic facial appearance.

Question 8

what are the InV for MEN2B ?

Answer 8

• Genetic screening for point mutations of the RET gene has 100% accuracy for identifying carriers (before biochemical abnormalities).
• Affected children are offered total thyroidectomy at an age related to the individual risk of each mutation (as early as 3y old for some aggressive mutations).
• Biochemical screening with 24h urine excretion of catecholamines and metanephrines and serum calcium and PTH are measured annually.

Question 9

what are the types of throid cancer?

Answer 9

papillary - 80%. usually well differentiated with tendency for lymph node involvement

Follicular - 10%. Spreads via direct haematogenous spread rather than LN’s.

Medullary - 4%. Originates in parafollicular C cells.

Anaplastic: an undifferentiated neoplasm with mitosis and vascular invasion. It usually presents with local encroachment into the recurrent laryngeal nerve and trachea, muscle, and/or oesophagus.

Lymphoma: generally a B cell-type non-Hodgkin’s lymphoma. It generally arises in the setting of pre-existing Hashimoto’s thyroiditis.

Question 10

what are the S&S of thyroid cancer and its red flags?

Answer 10

Thyroid cancers may present as a palpable lump, multiple lumps, or be found incidentally on imaging of the neck.

The red flag signs to be aware of with any neck lump that may suggest a malignancy are:
• Rapid growth
• Pain
• Cough, hoarse voice, or stridor
• Multiple enlarged cervical lymph nodes
• Tethering of the lump to surrounding structures

Question 11

what InV are done in suspected thyroid cancer?

Answer 11

TFTs (free T4, TSH levels). Should be normal.

Thyroid autoantibodies. Again normal.

Fine needle aspiration biopsy (FNAB). Mandatory for all thyroid nodules. An 18G needle is used to obtain a sample for cytological analysis

Neck ultrasound. Sometimes used to assess the size and characteristics of a nodule and to determine whether the nodule is solitary or part of multinodular goitre.

Question 12

what is the grading system for thyroid cancer?

Answer 12

• Thy1, non-diagnostic sample (though this may be expected if the nodule contains cystic fluid).
• Thy2, benign colloid nodule.
• Thy3, follicular lesion (i.e. either an adenoma or a carcinoma, the distinction being possible only after excision biopsy and histological analysis).
• Thy4, suspicious, but not diagnostic of papillary cancer.
• Thy5, diagnostic for thyroid cancer.