Endocrine Disorders Flashcards
What is the anatomy of the pituitary?
o Anterior pituitary = epithelial cells
§ Blood supply from portal system
o Posterior pituitary = nerve cells
§ Nerves from supraoptic and paraventricular nuclei
§ Release ADH and oxytocin
What is the anterior pituitary made of?
o Composed of epithelial cells from the developing oral cavity
o Secrete hormones that are under the influence of control factors released by the hypothalamus
What are the symptoms of pituitary disease?
o Hyperpituitarism
§ Excess secretion of trophic hormones
§ Usually due to a functional adenoma
o Hypopituitarism
§ Deficiency of hormones
o Local mass effect
What are the adenoma growths?
o 30% prolactinoma, 15% ACTH-oma, 15% GH-oma
o 20% non-functioning adenoma
How do we classify tumours?
Classified on basis of the hormones produced
o Detected by immunohistochemistry
o Prolactinoma most frequent
o N.B. “null cell” produces no hormones
What is the epidemiology of tumours?
o Pituitary adenomas = ~10% overt intracranial tumours
o Discovered incidentally in up to 25% of autopsies
o Age: 30-50 years
o Defined as a ‘microadenoma’ if <1 cm
What are the clinical effects of the functioning pituitary adenomas?
o Prolactinomas
§ Amenorrhoea, galactorrhoea, loss of libido, infertility
§ Usually diagnosed quicker in females of reproductive age
o Growth Hormone Adenomas
§ Prepubertal children -> gigantism
§ Adult -> acromegaly
§ Diabetes, muscle weakness, hypertension, congestive cardiac failure
o Corticotroph Cell Adenomas
§ Cushing’s disease
What is hypopituitarism caused by?
Most cases are caused by:
o Non-secreting pituitary adenoma
o Ischaemic necrosis -> MOST COMMONLY post-partum (Sheehan syndrome)
§ This is because the pituitary enlarges during pregnancy and is more susceptible to ischaemia
§ If you get a post-partum haemorrhage (Sheehan syndrome) you may develop ischaemia
§ Other causes… DIC, sickle cell anaemia, elevated ICP, shock
o Iatrogenic: ablation of pituitary by surgery or irradiation
What are the clinical features of hypopituitarism?
o Children – growth failure (pituitary dwarfism)
o Gonadotrophin deficiency
§ Amenorrhoea and infertility in women
§ Decreased libido and impotence in men
o TSH and ACTH deficiency – secondary hypothyroidism and secondary hypoadrenalism
o Prolactin deficiency – failure of post-partum lactation
What are the posterior pituitary syndromes?
Posterior pituitary syndromes = 2 peptides released by the posterior pituitary:
o ADH -> deficiency, insensitivity, excess -> DI or SIADH
o Oxytocin
What is the Local Mass Effect of Pituitary Tumours?
· Compression of optic chiasm gives rise to bitemporal hemianopia
· As the tumour gets larger, you may get features of raised ICP (e.g. headaches)
o In severe cases, you may get obstructive hydrocephalus
What is the thyroid gland?
· The follicles have a small amount of stromal tissue in between them
· Follicles lined by epithelial cells and have lots of colloid in the middle
· Parafollicular cells are found in between the follicles
What is the physiology of thyroid?
o In response to TSH, follicular epithelial cells pinocytose the colloid and convert thyroglobulin into T4 and T3
o T4 and T3 are released into the circulation and they increase basal metabolic rate
o Parafollicular cells (C cells) produce calcitonin which promotes the absorption of calcium by the skeletal system
What is a non toxic goitre?
enlargement without overproduction of thyroid hormones
§ Common if there is impaired synthesis of thyroid hormones (most often due to iodine deficiency)
· There are certain parts of the world where iodine intake is low (developing countries)
§ May be seen during puberty in girls
§ Ingestion of some substances that interfere with thyroid hormone synthesis can cause it (e.g. brassicas)
§ May be due to hereditary enzyme deficiency
What is a multinodular goitre?
§ With time, simple thyroid enlargement may be transformed to multinodular pattern
§ May become massive and cause mechanical effects such as dysphagia and airway obstruction
§ A hyperfunctioning nodule may develop -> hyperthyroidism
What are the causes of thyrotoxicosis?
o Primary Causes
§ Graves’ disease Hyperfunctioning multinodular goitre
§ Hyperfunctioning adenoma Thyroiditis
o Secondary Causes
§ TSH secreting pituitary adenomas (RARE)
o Causes that are NOT associated with the thyroid gland
§ Struma ovarii (ovarian teratoma with ectopic thyroid)
§ Factitious thyrotoxicosis (exogenous thyroid intake)
What is Graves’?
§ MOST COMMON cause of endogenous hyperthyroidism; mostly in FEMALES (7x)
§ Triad presentation: Thyrotoxicosis Exophthalmos Pretibial myxoedema
§ Autoimmune disorder associated with a variety of antibodies to the TSH-R and thyroglobulin
· They stimulate thyroid hormone release and increases proliferation of the epithelium
§ Associated with other AI diseases (SLE, pernicious anaemia, T1DM and Addison’s disease)
§ NOTE: autoimmune diseases of the thyroid gland are a SPECTRUM (from Graves to Hashimoto’s)
· Antibodies against thyroid antigens are common to both conditions but they differ in functio
What are the causes of hypothyroidism?
o Primary Causes
§ Post-ablative (after surgery or radioiodine therapy) Autoimmune (Hashimoto’s)
§ Iodine deficiency Congenital biosynthetic defect
o Secondary Causes
§ Pituitary or hypothalamic failure (UNCOMMON)
o Hashimoto’s Thyroiditis (the opposite of AI disease from Graves’ disease)
§ Common; F>M; 45-65yo Anti-TG ABs
§ Painless enlargement Anti-TPO ABs
§ Histology à lot of lymphoid cells with germinal centres
· Hurthle cells = epithelial cells become large with lots of eosinophilic cytoplasm
· Lymphoid cells = chronic infection / A
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