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
What are the six clinical signs of anterior pituitary hyperfunction leading to cushing’s disease?
Pot-belly
Alopecia
Polyuria
Polyphagia
Calcinosis cutis
Muscle wastage
What type of control is exerted on the pars intermedia in a normal, healthy horse?
In healthy, normal horses the pars intermedia is under dopaminergic control from the hypothalamus
How does the dopaminergic control of the pars intermedia differ in autumn in normal, healthy horses?
In the autumn, most healthy horses have a decrease in dopaminergic control of the pars intermedia which allows for increased growth of the hair coat and increased fat deposition
What is equine pars intermedia dysfunction (PPID)?
Equine pars intermedia dysfunction (PPID) is when there is decreased dopaminergic control exerted on the pars intermedia all year round. Without this inhibition, melanotrophs of the pars intermedia synthesise excessive hormone in combination with hyperplasia and the development of micro- and macro-adenomas. This can cause compression of the hypothalamus which can contribute to clinical signs
Which age group of horses are commonly affected by equine pituitary pars intermedia dysfunction (PPID)?
Older horses (15 years and older)
What are the ten clinical signs of equine pituitary pars intermedia dysfunction (PPID)?
Polyphagia
Polyuria
Polydipsia
Hyperglycaemia
Insulin resistance
Laminitis
Generalised hyperhidrosis (excessive sweating)
Somnolence
Hypertrichosis (abnormal hair growth)
Abnormal fat deposition
What is equine metabolic syndrome (EMS)?
Equine metabolic syndrome (EMS) is a condition characterised by abnormal fat deposits particularly around the neck and tail head and insulin resistance, both of which predisposing the affected individual to laminitis
What causes equine metabolic syndrome (EMS)?
Equine metabolic syndrome (EMS) is caused by the excessive production of adipokine hormone by adipose tissue, resulting in increased cortisol production. This abnormal hormone production disrupts the body’s normal response to insulin, resulting in hyperglycaemia and insulin resistance
Which age group of horses are commonly affected by equine metabolic syndrome (EMS)?
Young horses
Which three factors should you consider to differentiate equine pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS)?
Age of onset
Additional clinical signs associated with equine pituitary pars intermedia dysfunction (PPID)
Positive diagnostic test for equine pituitary pars intermedia dysfunction (PPID)
(T/F) Horses can have both equine pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS) at the same time
TRUE.
What are the two other names used to describe adrenal cortical hypofunction?
Hypoadrenocorticism
Addison’s disease
With adrenal cortical hypofunction which three hormones will have decreased secretion?
Aldosterone
Cortisol
Androgens
What are the consequences of decreased aldosterone production due to adrenal cortical hypofunction?
Decreased aldosterone production will increase renal potassium retention and renal sodium excretion causing hyperkalaemia and hyponatraemia resulting in polyuria and polydipsia
What are the consequences of decreased cortisol production due to adrenal cortical hypofunction?
Decreased cortisol production will lead to a lack of appropriate immune response resulting in poor wound healing, increased susceptibility to secondary infection and cause the individual to lack a stress leukogram. Furthermore, decreased cortisol production causes vomiting, diarrhoea, weakness and a poor body condition score
What are the consequences of decreased androgen production due to adrenal cortical hypofunction?
Decreased androgen production causes sub-fertility
What are the four main causes of adrenal cortical hypofunction?
Idiopathic
Atrophy
Damage to the adrenal cortex
Secondary to anterior pituitary hypofunction
Which two breeds of dog are genetically predisposed to adrenal cortical hypofunction?
Bearded collies
Portugese Water dogs