Nuts and Bolts of Endocrine system histology Flashcards
Endocrine
Hormone acts on target organ away from the secreting cell
Autocrine
Hormone acts on secreting cells
Paracrine
Hormone acts on adjacent cells
Neuroendocrine
Neural stimulation of endocrine cells to secrete hormones e.g. adrenal medulla
Typical structure of endocrine glands
Cuboidal secretory cells with a lumen
Secretory cells supported by myoepithelium
Acidophilic cells of the anterior pituitary
Take up acidic dyes
Somatotrophes
Lactotrophes
Basophilic cells of the anterior pituitary
Take up basic dyes
Thydrotrophes
Gonadotrophes
Corticotrophes
Chromophobic cells of the anterior pituitary
No specific staining features
Corticotrophes
Pituitary adenoma
Arises from anterior lobe
Functional - hyperpituitarism due to overproduction
Non-functional - hypopituitarism due to pressure effect
Symptoms of pituitary adenoma
Headache Vomiting Nausea Diplopia Impaired vision e.g. bilateral hemianopsia
Lack of iodine
Causes goitre
Thyroid enlarges to absorb the maximum concentration of iodine
Thyroid gland structure
Composed of follicles with cuboidal cells containing colloid and with variable sized lumina
Fenestrations between endothelial cells allow hormone to enter bloodstream
Parafollicular/clear/C cells secrete calcitonin to decrease calcium concentration in blood
Origin of medullary carcinoma of thyroid
Parafollicular/clear/C cells
Euthyroid pathology
Goitre
Adenoma
Carcinoma
Hyperthyroid pathology
Grave’s disease
Hypothyroid pathology
Hashimoto’s disease
Tracheomalacia
Softening and collapse of trachea to obstruct airways
Can occur following thyroidectomy if goitre was compressing trachea
Grave’s disease
Auto-antibodies stimulate TSH receptors to cause diffuse goitre
Increased T3/T4 and decreased TSH (hyperthyroidism)
Infiltrative ophthalmopathy - accumulation of soft tissue and inflammatory cells behind eyes to cause proptosis
Infiltrative dermopathy - causes pre-tibial myxoedma (thickening and hardening of skin on anterior shin, may have oedema)
Hashimoto’s thyroiditis
Autoimmune disease causing progressive destruction of the thyroid due to inflammation, tissue replaced by fibrosis
Low T3/T4, high TSH, prominent lymphatic infiltration/inflammation
Thyroid tumours
Benign follicular adenoma
Papillary/follicular/medullary/anaplastic carcinomas
Parathyroid pathology
Cause hypercalcaemia:
Adenoma affecting 1 gland
Hyperplasia affecting 4 glands
Histological appearance of zona glomerulosa
closely packed round cells
Histological appearance of zona reticularis
small dark staining cells
Histological appearance of zona fasciculata
clear cells arranged in cords
Causes of adrenocortical hyperactivity
Hyperplasia Adenoma (non-functioning may cause Cushing's syndrome or Conn's syndrome) Cancer (rare) Cushing's syndrome (excess cortisol) Conn's syndrome (excess aldosterone) Androgenital syndrome (excess androgens)
Causes of adrenocortical insufficiency
Addison’s disease
Phaeochromocytoma
Tumour of adrenal medulla with increased catecholamine levels
Causes of phaeochromocytoma
Treatable hypertension
Tumour (MEN2, extra-adrenal, malignant, bilateral)
Genetic causes: Von-Hippel Syndrome (retinal tumour), Multiple Endocrine Neoplasia type 2(MEN2 - thyroid medullary tumour), Neurofibromatosis type 1 (NF1)
Treatment of phaeochromocytoma
Prescribed antihypertensive to block affects of high adrenaline and risk of dangerously high blood pressure during surgery (alpha or beta blockers given)
Surgical excision of tumour
Symptoms and signs of phaeochromocytoma
Hypertension Tachycardia Palpitations Headache Sweating Tremor Sense of apprehension
Complications of high BP in phaeochromocytoma
Congestive cardiac failure
Cerebrovascular accident
Ischaemic heart disease
Arrhythmia
Cushing’s syndrome vs Cushing’s disease
Cushing’s syndrome refers to the condition caused by excess cortisol in the body, regardless of the cause. When Cushing’s syndrome is caused by a pituitary tumour, it is called Cushing’s disease.
