PATHOLOGY - Endocrine System Flashcards
What is endocrine signalling?
Endocrine signalling is the synthesis and secretion of signalling molecules (hormones) by endocrine cells into the bloodstream to act on target cells at distant body sites
What is endocrine hypofunction?
Endocrine hypofunction refers to a decreased or underactive function of an endocrine gland, resulting in reduced hormone production
What are the three possible mechanisms of primary endocrine hypofunction?
Failure of endocrine gland development
Destruction of secretory cells
Biochemical defect in the synthetic pathways
What is the main mechanism of secondary endocrine hypofunction?
The main mechanism of secondary endocrine hypofunction involves damage to the endocrine tissue, which leads to a decrease in trophic hormone secretion. This decrease in trophic hormones then affects the target organ’s hormone production
What is endocrine hyperfunction?
Endocrine hyperfunction refers to an increased or overactive function of an endocrine gland, resulting in excessive hormone production
What is the main mechanism of primary endocrine hyperfunction?
The main mechanism of primary endocrine hyperfunction involves abnormal cells within the endocrine glands producing excessive hormones
Usually functional/non-functional neoplasia and hyperplasia
What is the main mechanism of secondary endocrine hyperfunction?
The main mechanism of secondary endocrine hyperfunction involves abnormal cells within endocrine glands producing excessive trophic hormones. This excess of trophic hormones then causes excessive hormone production by the target organ
What are the consequences of anterior pituitary hypofunction?
Anterior pituitary hypofunction will result in decreased follicle stimulating hormone (FSH), luteinising hormone (LH), thyroid-stimulating hormone (TSH), growth hormone (GH) and adrenocorticotropic hormone (ACTH). Reduced FSH and LH will result in sub-fertility and infertility, reduced TSH will result in hair coat, metabolism and growth abnormalities, reduced GH will result in metabolism and growth abnormalities and reduced ACTH will result in reduced cortisol production by the adrenal glands, leading to delayed parturition and altered metabolism and growth
What are the six possible causes of primary anterior pituitary hypofunction?
Aplasia
Hypoplasia
Abscesses
Granulomas
Cystic Rathke’s pouch
Neoplasia
What is the possible cause of secondary anterior pituitary hypofunction?
Hypothalamic malfunction
Give an example of a disease caused by anterior pituitary hypofunction?
Pituitary dwarfism
What are the five main clinical signs of pituitary dwarfism?
Decreased growth rate
Abnormal hair growth (retain puppy coat followed by bilateral, symmetrical alopecia and hyperpigmentation)
Hypoplasia of gonads and genitalia
Permanent deciduous dentition
Delayed epiphyseal growth plate closure
Which breed of dog is suscepible to pituitary dwarfism?
German Shepherd
Why are German Shepherds susceptible to pituitary dwarfism?
German Shepherds have an autosomal recessive inherited disorder resulting in cystic Rathke’s pouch causing primary anterioir pituitary hypofunction resulting in pituitary dwarfism
What is the clincial term for posterior pituitary hypofunction?
Diabetes insipidus
What is central diabetes insipidus?
Central diabetes insipidus is caused by hypofunction of the posterior pituitary gland, resulting in reduced antidiuretic hormone (ADH) secretion. Antidiuretic hormone (ADH) is responsible for increasing the permeability of the collecting ducts in the nephrons of the kidney to increase the reabsorption of water and allow for the concentration of urine. Where there is antidiuretic hormone (ADH) deficiency, it will lead to large volumes of dilute urine, hypernatraemia and dehydration
What is nephrogenic diabetes insipidus?
Nephrogenic diabetes insipidus is a condition where the kidneys are unable to respond to antidiuretic hormone (ADH)
How does diabetes insipidus cause hypernatraemia?
Diabetes insipidus causes excessive urination and dehydration which can lead to hypernatraemia as the body is losing more water relative to sodium, causing an imbalance
What are the three clinical signs of central and nephrogenic diabetes insipidus?
Polyuria
Polydipsia
Low urine specific gravity (USG)
Which two tumours most commonly cause primary pituitary hyperfunction?
Adenoma
Adenocarcinoma
What is the most common cause of primary pituitary hyperfunction in dogs?
Adenoma in the anterior pituitary gland (pars distalis)
What is the most common cause of primary pituitary hyperfunction in horses?
Adenoma in the pars intermedia
What are the consequences of anterior pituitary hyperfunction?
Anterior pituitary hyperfunction leads to excessive adrenocorticotropic hormone (ACTH) production which will stimulate excessive cortisol production in the adrenal glands, causing cushing’s disease. Excessive cortisol causes polyuria, alopecia, immune supression which makes the animal more susceptible to secondary infection, increases protein catabolsim causing muscle wasting, increased appetite and increased glycogen metabolism in the liver causing vacuolar hepatopathy
Describe what vacuolar hepatopathy looks like on a histological slide
There will be the presence of both vacuoles and hepatocytes, the vacuoles will appear as small, clear spaces within the hepatocytes