Endocrine System Flashcards
Name some examples of endocrine glands
Hypothalamus Anterior/posterior pituitary Thyroid Parathyroid Adrenal cortex and medulla Pineal gland Testes/ovaries/placenta Pancrease Kidneys/liver/GIT/thymus
True or false
The endocrine system has ducts
FALSE
the endocrine system is a group of ductless glands
What are the functions of the endocrine system
Maintaining homeostasis
Driving change (growth/lactation/pregnancy)
How does the endocrine system fulfill its functions
By releasing hormones
Endocrine glands ____, ___ and then ___ hormones directly into the bloodstream
Synthesize
Store
Secrete
What are hormones
Chemical messengers
Communication and control molecules
When are hormones secreted
In response to a stimulus
True or false
Any hormone can bind to any receptor
FALSE
hormones have specific receptors at specific target organs (these receptors only respond to their specific hormone)
Secretion of hormones is mainly controlled by
Negative feedback
What is negative feedback
A feedback mechanism resulting in the inhibition or slowing of a process
Ex. Signals are sent to stop or decrease production/release of hormones
What else can secretion of hormones be controlled by
Positive feedback
Nervous stimulation
What is positive feedback
Senses something which increases production/secretion
Ex. Nursing stimulates prolactin release with stimulates more milk production
What is nervous stimulation in hormone secretion
The sympathetic nervous system causes a release of adrenalin (epinephrine) during the fight or flight response
Or
Physical stimulation causes the release of a hormone (oxytocin)
What are some characteristics of the hypothalamus
Part of the base of the brain
Links the cerebrum to the endocrine
system (consciousness of hormones)
Regulates appetite, body temp, and sleep and wake cycles
How is the hypothalamus connected to the pituitary gland
The pituitary is a gland attached to the base of the hypothalamus by a thin stalk of nerves and blood vessels
What is the “master gland” of the endocrine system
The pituitary gland
The blood vessels form a portal system between the ____ pituitary and the hypothalamus
Anterior
Explain the portal system between the hypothalamus and the anterior pituitary
When the hypothalamus recieves a stimulus from the CNS it secretes hormones into its portal system to regulate pituitary hormone secretion
What is a portal system
Vessels that begin and end in the capillaries, a way to transport secretions directly from one tissue to another
The nervous connection between the posterior pituitary and the hypothalamus allows
Direct transport of oxytocin and antidiuretic hormone (ADH)
(These are made in the hypothalamus and stored in the posterior pituitary and released on stimulation by nerve impulses from the hypothalamus)
What kind of hormones does the hypothalamus release
Releasing or inhibiting hormones that affect the secretion of another hormone
What are some characteristics of the pituitary gland (hypophysis)
Controls other endocrine glands
Size of a small pea/bean
Attached to hypothalamus by a stalk and seated in a pocket of the sphenoid bone of the skull
Has a glandular anterior portion and a nervous posterior portion
How many hormones does the anterior pituitary produce and what are they
7 Growth hormone Prolactin Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle stimulating hormone (FSH) Luteinizing hormone (LH) Melanocyte stimulating hormone (MSH)
The release of hormones from the anterior pituitary is controlled by what
The appropriate releasing or inhibiting hormone from the hypothalamus
What does growth hormone do (somatotropin or somatotropic hormone)
Promotes body growth in young animals (bone and muscle)
Regulates metabolism of proteins, carbohydrates and lipids
Anabolism of proteins for growth, regeneration and repair of tissue
Mobilization of lipids from storage and catabolism for energy
Promotes glycogenolysis and minimizes catabolism of glucose (promotes hyperglycemia)
What does a deficiency in growth hormone cause
Dwarfism
Alopecia
Thin skin
Secondary abnormalities of thyroid, adrenal and reproductive hormones
What is pituitary dwarfism
When dwarfism is caused by a deficiency in growth hormone
Small body with regular proportions
What does an excess in growth hormone cause
Giantism: excess hormone WHILE GROWING (exaggerated bone growth)
Acromegally: excess hormone when MATURE (growth plates are closed so you see cartilage proliferation around joints and facial changes) see large noses, lips and forheads
What does supplementation of bovine somatotropin (BST) do in the US dairy industry
What are some side effects
Increases milk production by 10%
Side effects: increased body temp, reduced fertility, risk of mastitis and digestive disorders because nutrients are diverted to milk production
What is prolactin
Helps trigger and mantain lactation
Secretion of prolactin and lactation are maintained as long as physical stimulation of nursing or milking continues
Animals will “dry up” if it stops (weaning)
From the anterior pituitary
What is thyroid stimulating hormone (AKA: thyrotropin or TSH)
Stimulates the thyroid gland to produce thyroid hormones
Regulated by the hypothalamus which releases TSH-releasing hormone
Secreted from the anterior pituitary
What happens to thyroid stimulating hormone if thyroid levels drop
Thyroid stimulating hormone will increase
What happens if thyroid hormone levels rise
Negative feedback reduces TSH production to then decrease thyroid hormone
What is adrenocorticotropic hormone (ACTH)
Stimulates the adrenal cortex
Controlled by negative feedback
During stress, the CNS sends signals through the hypothalamus for the release of ACTH-RH which causes release of ACTH from anterior pituitary which then causes release of cortisol and other “stress” (steriod) hormones from the adrenal cortex
What is the folicle stimulating hormone’s (FSH) role in females
Stimulates growth and development of ovarian follicles and oocyte production. Also stimulates the follicle to release estrogen
Promotes physical and behavioural changes of estrus
Released from the anterior pituitary
What is the folicle stimulating hormone’s (FSH) role in males
Stimulates growth and development of sperm (spermatogenesis)
Also has a minor role in estrogen production
Why is FSH used in animal production
To increase the number of follicles that develop
Causes the release of more than one egg
Allows some to be harvested for freezing and/or embryo transfer
What is luteinizing hormone (LH)
Ripening hormone for the follicle
Estrogens feeback to the pituitary to eventually decrease FSH and increase LH (estrogens from the follicle)
Causes the final rupture and release of the egg from the follicle
Also maintains the corpus luteum
What happens after the egg is released
The cells of the empty follcile develop into the corpus luteum and release progestins (progesterone) to help maintain pregnancy
What is LH’s role in males
Can be called interstitial cell stimulating hormone
Encourages production of testosterone
What are FSH and LH examples of and why
Gonadotropins
They stimulate the development and growth of the gonads
What is melanocyte-stimulating hormone (MSH)
Uncertain role in most animals at normal levels
Can cause skin to darken at high levels
In reptiles/fish/amphibians it causes rapid changes in color
What are some characteristics of the posterior pituitary
Does NOT produce any hormones
Stores and releases 2 hormones produced by the hypothalamus, they get to the posterior pituitary by transport down nerve fibers
Release is directed by the hypothalamus
What hormones does the posterior pituitary produce
Antidiuretic hormone (ADH) and oxytocin
What does antidiuretic hormone do
Reduces urination and encourages conservation of water (prevents diuresis) by encouraging kidneys to increase absorption of water from the urine
By increasing water absorption from urine what happens to the urine
Urine becomes concentrated, darker and stronger smelling (less water)
When is ADH secreted
When the animal is dehydrated
And
When the hypothalamus senses hemoconcentration (more concentrated RBC in blood but a decrease in volume) which signals the pituitary to release the ADH which then affects the kidneys, this is to put for water in the vessels
How does caffine and alcohol affect thirst
These inhibit ADH (so increases urination) so they do not quench thirst
What does a deficiency of ADH cause
Diabetes insipidus
Animals become PU/PD because they can’t concentrate their urine
How do you treat a deficiency in ADH
ADH mimicking drugs
Difference between diabetes mellitus and insipidus
Diabetes mellitus Hormonal deficiency: insulin Glucose in urine: yes Urine in specific gravity: high Urine volume: increased
Diabetes insipidus Hormonal deficiency: ADH Glucose in urine: No Urine in specific gravity: low Urine volume: increased
What does oxytocin do
Causes contraction of the uterine muscles at breeding (moves sperm up to the oviduct) and parturition (helps deliver the fetus and placenta)
Used to promote bonding during fostering
Causes milk let down in lactating females (moves milk to the lower part of the mammary gland)
What is release of oxytocin stimulated by
Sensory stimulation of nursing, intromission or the fetus at birth
Can also be associated with moving into the milking barn
Why is oxytocin used as a drug
To promote delivery of the fetus, placenta or milk
What are some characteristics of the thyroid gland
Two lobes, sometimes connected
Located on either side and just below the larynx
Composed of thousands of tiny follicles (spheres of cells around a central area) containing the thyroid hormone precursor called colloid
What hormones does the thyroid gland produce
Thyroid hormone and calcitonin
Thyroid hormone is produced in 2 forms
T3 and T4
Named for how many iodine atoms they have per molecule of hormone
Produced in response to TSH from anterior pituitary
T4 is also called thyroxine, the main form produced by the gland
True or false
T3 is the more physiological active form of thyroid hormone and is produced from T4 in tissues
True
What are the 3 metabolic effects of thyroid hormone
Calorigenic effects
Effect on protein, carbohydrate and lipid metabolism
Cardiovascular effects
What is the calorigenic effect of thyroid hormone and when is production increased or decreased for these effects
Helps heat the body by increasing metabolic rate
Production is increased with exposure to cold
Production is decreased by emotional or physical stress (makes more susceptible to cold)
What is thyroid hormones effect on protein, carbohydrate and lipid metabolism
Stimulates protein anabolism if nutrition is adequate. Catabolism of proteins if the animals is starving and thyroid levels are high
Encourages lipid catabolism
Tends to cause hyperglycemia
What is the thyroid hormone’s cardiovascular effect
Increases heart rate
What are the developmental effects of thyroid hormone
Necessary for young growing animals
Helps maturation of CNS and growth and development of muscles and bones
What is a goiter (caused by thyroid hormone)
Non cancerous thyroid gland enlargement usually caused by iodine deficiency
Thyroid gland becomes hyperplastic, enlarged but there is still deficient amounts of T3 and T4 (hypothyroid)
Why does a deficiency in iodine cause goiters
Iodine is a component of thyroid hormones, therefore if it is deficient, the body cant make T3 or T4
This decreased T4 makes the pituitary increase TSH levels
How do you treat goiters
Diets supplemented with iodized salt or treat with betadine
What is hypothyroidism (may or may not also have a goiter)
Most common in adult dogs (acquired)
Low levels of T3 and mainly T4
What are the signs of hypothyroidism
Alopecia Dry skin Lethargy Weight gain Heat seeking Slow heart rate
All related to decreased metabolic rate
What happens if hypothyroidism occurs in young animals
Causes dwarfism or cretinism
Stunted growth, abnormal bone formation, mental retardation, sluggishness
How do you treat hypothyroidism
Thyroid supplements
What is hyperthyroidism
Most common in cats
High levels of T4 and T3
What are the signs of hyperthyroidism
Nervousness Irritability Weight loss (but increased appetite) because of heat melting fat Fast heart rate Vomiting Diarrhea Polyuria/polydipsia
How do you treat hyperthyroidism
Surgical removal of the gland
Medication to inhibit thyroid hormone production (often for life)
Radioactive iodine
What is calcitonin and what does it do
Produced by C-cells found between the thyroid follicles
Functions to keep blood calcium levels from getting too high
Stimulates storage of excess blood calcium in the bones
Lowers blood calcium
What are the characteristics of the parathyroid gland
Variable in appearance and location
Normally found on or near the thyroid
Paired, one pair on the surface of the thyroid, other within the thyroid
Appear as small pale nodules
Produces one hormone
What is the parathyroid hormone
(AKA: PTH or parathormone) and what does it do
Functions to keep blood calcium levels from getting too low by increasing renal retention, intestinal absorption and bone calcium mobilization
(Increases blood calcium)
Also promotes the formation of the active form of Vit D in the kidneys
What are some examples of when PTH is inadequate causing blood calcium levels to fall (life threatening) and how do you treat it
Milk fever in cattle (low calcium levels due to lactation) (muscle weakness and “downer cows”)
Low calcium causes Eclampsia in dogs/cats/humans (muscle tremors, spasms and seizures)
Treat with administration of IV calcium and continue with supplements after crisis
What does chronic excessive PTH cause
Weakens bones (osteoporosis)
What is nutritional secondary hyperparathyroidism
Diet deficient in calcium causes low blood calcium levels and increases release of PTH to mobilize it from bones
Results in osteoporosis (weak bones) in adults
In growing animals it causes weak bones and deformities called Rickets
What is nutritional secondary hyperparathyroidism called in horses, what do you see and what is it from
Bighead disease or Bran disease
From being fed high cereal by products, bran diets, which are low in calcium
Bone that is reabsorbed is replaced by soft fibrous tissue
Most noticeable on the flat bones of the skull and mandible (often see a big head)
What are some characteristics of the adrenal glands
Paired
Found near the cranial end of kidneys
Composed of an outer adrenal cortex and an inner adrenal medulla
What is the adrenal cortex
The outer layer of the adrenal gland
Composed of typical glandular tissue
Makes 3 types of hormones collectively called steroid hormones
Makes Mineralocorticoid, glucocorticoid and sex hormones
What are mineralocorticoid hormones (aldosterone)
Regulates mineral salt (electrolyte) levels
Increases blood sodium, decreases potassium and hydrogen ions through effects on the kidneys (effects the filtrate that will end up as urine)
Release of mineralocorticoid hormones is stimulated by the renin-angiotensin system, what is this
When the macula densa senses decreased sodium concentration, and/or the juxtaglomerular apparatus senses decreased blood flow or pressure to the kidneys, it stimulates the release of renin from the juxtaglomerular apparatus
Renin catalyzes the conversion of angiotensinogen into angiotensin 1
Angiotensin 1 is converted to angiotensin 2
Angiotensin 2 stimulates the release of aldosterone from the adrenal cortex
Aldosterone increases salt (and water) absorption from the kidneys and causes vasocontriction, all increases blood pressure and sodium concentrations
What are ACE inhibitors
A class of heart medications used to decrease BP by inhibiting the angiotensin converting enzyme
Also used to treat chronic renal disease (improves renal blood flow as afferent arterioles are no longer constricted)
What are glucocorticoid hormones
Increase blood glucose
Includes: cortisone, cortisol, corticosterone
Associated with stress responses
Helps maintain BP
Mobilizes proteins and fats and promotes gluconeogenesis in the liver
Has anti-inflammatory effects
Drugs like prednisone, dexanethasone, triamcinolone and hydrocortisone mimic the effects of glucocorticoids. What are these often used for and what are the side effects of iatrogenic hyperadrenocorticism
Used to control inflammation
Polyuria/polydipsia Immunosuppression Altered WBC counts Delayed wound healing Catabolism of proteins (fading) Abortion Hyperglycemia Suppresion of normal adrenal cortical secretions
Mainly used in LA for affect in blood glucose, and SA for anti-inflammatory effects
What can hypoadrenocorticism cause
Low sodium, high potassium, low HR and BP, weakness, and can be life threatening
Mainly due to a deficiency of mineralocorticoid hormones
What sex hormones do the innermost layers of the adrenal cortex produce
Small amounts of androgens and estrogens with minimal systemic effects (not a major site of production)
May play a role in some tumors
What is the adrenal medulla
Nervous tissue organ of the adrenal gland
Hormone secreting cells are modified neurons
Produces mainly epinephrine and some norepinephrines
Responds to sympathetic stimulation
Fight or flight response
What are the effects of hormones and direct sympathetic NS stimulation during the stress response
Increased HR, cardiac output, BP, RR
dialted airways (bronchodilation)
Decreased GI motility
Increase blood glucose
What are the characteristics of the pancreas
Long flat organ runs along the duodenum
Has both exocrine and endocrine functions
Exocrine: secretes digestive enzymes into the duodenum
Endocrine: pancreatic islets: thousands of tiny clumps of cells scattered in the pancreas, called the islets of langerhans, 3 different islets produce its own distinct hormone
What three hormones does the pancreas secrete
Insulin
Glucagon
Somatostatin
What is insulin and what does it do
Vital to life
Allows cells to absorb glucose (by increasing transport proteins on the cell membrane)
Increases glycogen production in liver and muscles
Increases protein and fat synthesis
Primarily effect is to lower blood glucose
What is glucagon and what does it do
Not as vital as insulin because other hormones have similar effects
Raises blood glucose
Stimulates glycogenolysis and gluconeogenesis
What is somatostatin
Inhibits secretion of insulin, glucagon and growth hormone
Decreases GI motility
What are some characteristics of the testes
Paired organs found in the scrotum
Mostly coiled seminiferous tubules -which continuously produce sperm
Between the tubules are interstitial cells (endocrine cells)
What do the interstitial cells of the testes produce
Androgens -primarily testosterone
What is testosterone important for
Important for development of male secondary sex characteristics (muscles, libido, accessory glands, growth of penis)
Maturation of sperm
Overal metabolic effect is anabolic (muscle formation)
Production stimulated by LH from anterior pituitary
What are some characteristics of the ovaries and what do they produce
Paired organs found in the abdomen behind the kidneys
Have a cyclical production of hormones and ova controlled by FSH and LH
Produces Estrogens and progestins
What is estrogen and what does it do (from the ovaries)
Mainly estradiol and estrone
Produced by developing follicle cells in response to FSH
Cause physical and behavioural changes of estrus (in prep for breeding and pregnancy)
ovulation occurs at/just after LH peak
As levels of estrogen increase, they feedback to pituitary and ___ FSH and ____ LH
Decrease FSH
increase LH
What are progestins and what do they do
Progesterone and related hormones
After ovulation, LH stimulates the empty follicle to develop into a corpus luteum
The corpus luteum produces progestins (like progesterone)
Important for maintaining pregnancy: prepares uterus for the egg and maintains ovum there once implanted
What happens to the corpus luteum If an animal becomes pregnant, what if they dont become pregnant
Pregnant: Persist due to feedback from the uterus
Not: it will regress and allow another follicle to develop
Why are progestins used as drugs
Supresses estrus
Synchronize estrus
Help maintain pregnancy (especially in mares)
What does prostaglandin F2-alpha cause
Luteolysis, reduces progestins and is used to synchronize or abort animals (in animals and humans)
What hormone does the kidney produce and what does it do
Erythropoietin (EPO)
Stimulates RBC production in response to hypoxia
Chronic renal failure is often accompanied by
Anemia due to decreased EPO production
May become life threatening (need a transfusion or EPO supplementation)
What hormone does the stomach produce, what does it do and what stimulates secretion of it
Gastrin
Stimulates HCl and digestive enzyme production and muscular contraction
Gastrin is stimulated by the presence of food in the stomach
What hormones does the small intestine produce and what stimulates secretion of them
Secretin and cholecystokinin (CCK)
Produced in response to entry of chyme from the stomach
What does secretin do
Stimulates pancreas to secrete bicarbonate to neutralize chyme
What does cholecystokinin do
Inhibits gastric secretions and gastric motility (slows down movement)
Stimulates gall bladder to contract and release bile
What is the main purpose of the placenta
Helps maintain pregnancy
What hormones does the placenta release
Estrogen
Progesterone
Chorionic gonadotropin
What is chorionic gonadotropin
Primarily in humans and horses
It is a LH like hormone that maintains the corpus luteum
It is used in some pregnancy tests
Describe the thymus, its role in young and adult animals, and what hormones it secretes
Important in developing immunity in young animals
Shrinks to a remnant in adulthood
Involved in development of T-lymphocytes important for cell-mediated immunity
Hormones include thymosin and thymopoietin
What hormone does the pineal body produce and what does it do
Melatonin
Affects sleep and wake cycles
May be linked to estrus
In fish/amphibians/repriles the pineal body is close enough to the thin skull top that it can respond to light (photosensitive)
In mammals, photoreceptors in the eyes relay info to the brain including the pineal body
True or false
Light at night disturbs sleep
True
What falls into the category of eicosanoids
Prostaglandins
Thromboxanes
Leukotrienes
Why are eicosanoids considered autacoid or paracrine
Instead of secreting into the bloodstream, they act locally staying close to the place of production
What are eicosanoids derived from
Unsaturated fatty acids
What are leukotrienes
Produced by WBCs
Associates with inflammation (increased vascular permeability and airways constriction)
What are thromboxanes important for
Blood clotting
What are the effects of prostaglandins (vary depending on type)
Vasodilation (decreases BP) GI smooth muscle contraction/relaxation Bronchoconstriction Renal blood flow and kidney function Platelet aggregation and blood clotting Promotes inflammation (PGE) Reproductive effects of PG
What does PGF2-alpha cause
Luteolysis and can cause abortion in early pregnancy or be used for estrus synchronization in live stock
What do NSAID typically block
Block production of leukotrienes/thromboxanes/prostaglandins
Ratio varies with the drug
What is giantism
Excessive growth as a result of excess growth hormone during developments (pre puberty)
What is acromegaly
What do you see
Excessive growth hormone when mature
Excess bone, cartilage and muscle growth
See enlarged skulls, hands and feet
What is different about pituitary dwarfism
Children are small in size but have normal body proportions
What is diabetes mellitus caused by
Insufficient insulin production by the pancreas leading to hyperglycemia
What are the predisposing factors of diabetes mellitus
Obesity
Endocrine diseases such as: cushing’s disease (hyperadrenocorticism)
hyperthyroidism
(both of which increase blood glucose and therefore cause hyperglycemia and both wear out pancreatic islets due to constant production of insulin)
Hypothyroidism (immune malfunction)
What are the clinical signs of diabetes mellitus
Polyuria/polydipsia
Increased appetite
Weightloss
Lethargy
Cataracts (after continuous exposure to high levels of glucose)
How is diabetes mellitus diagnosed
Detection of elevated blood glucose and glucose in the urine
How do you treat diabetes mellitus
Subcutaneous injections of insulin
Close monitoring of food intake, blood and urine glucose levels
Special diets may stabilize insulin levels and dosages
What are some complications associated with diabetes mellitus
Ketoacidosis: without insulin the body breaks fown fats producing ketones (see hyperglycemia, glucose and ketons in urine, anorexia, dehydration, vomiting, depression and collapse)
Bacterial infections (conjunctivitis and UTIs)
Insulin induced hypoglycemia: see restlessness, ataxia, muscle twitching and seizures. May cause comas and death
What is diabetes insipidus caused by
Failure of the kidneys to reabsorb water. Can be from a deficiency in antidiuretic hormone or failure of the renal collecting ducts to respond to ADH
What are the clinical signs of diabetes insipidus
Polyuria and polydipsia
Very dilute urine
How is diabetes insipidus diagnosed
By with holiding water and monitoring urine specific gravity
Administering a synthetic ADH and monitoring specific gravity of urine
What causes cushing’s disease (HYPERadrenocorticism)
Excessive administration of steroids (iatrogenic) or
by an over production of steroids by the adrenal cortex (normally due to pituitary or adrenal neoplasia)
What are the clinical signs of cushing’s disease
Polyuria and polydipsia
Increased appetite
Abdominal distension
Muscle atrophy and weakness
Lethargy
Thinning skin and alopecia
More susceptible to infections
How is cushing’s disease diagnosed
Blood tests which involve taking a base line blood sample, injecting ACTH and/or dexamethasone and then taking timed blood samples to monitor for cortisol levels
What happens in the most common form of cushing’s disease due to a pituitary tumor
The negative feeback system fails and the pituitary continues to produce ACTH despite the high cortisol levels in the blood
What is addison’s disease (HYPOadrenocorticism) caused by
Caused by reduction or failure of steroid (aldosterone) production by the adrenal cortex. This can be from neoplasia, atrophy of the adrenal cortex or long term steroid administration (iatrogenic)
What are the clinical signs of addison’s disease
Polyuria and polydipsia Anorexia Vomiting and diarrhea Hypotension Bradycardia and collapse
How is addison’s disease diagnosed
Blood tests for electrolyte imbalances (low sodium and high potassium) and ACTH stimulation test
What is the treatment for addison’s disease
Administration of glucocorticoids and mineralocorticoids
How does aldosterone affect the sodium potassium pumps
Inserts sodium potassium pumps into the lumen and activates the pump between the lumen and blood
Describe hyperthyroidism, the clinical signs, who is is normally seen in and the treatment
Increases thyroid activity (too much thyroxine)
Mainly seen in middle aged cats
Signs: hyperactivity, increased metabolic rate, nervousness, excitability, tachycardia, polyphagia, polyuria and polydipsia, weight loss
Treatment: surgical removal of the thyroid, radioactive iodine, chemotherapy drugs for life, prescription diets
Describe hypothyroidism, the clinical signs, who is is normally seen in and the treatment
Decreased thyroid activity (decreased thyroxine)
Mainly seen in middle aged dogs
Signs: letharygy, weakness, bradycardia, decreased metabolic rate, dermatological changes including alopecia, dry skin and hyperpigmentation, heat seeking
Treatment: thyroid hormone supplements for life
What is hyperparathyroidism caused by
Excessive parathyroid hormone secretion due to neoplasia of the parathyroid gland (primary) or renal disease (secondary) or nutritional deficiencies (secondary)
What does primary hyperparathyroidism cause and what are the signs
Increases blood calcium and tissue calcification
Signs: polyuria/polydipsia (due to renal damage from calcification), inappetance, lethargy and weakness
What is secondary hyperparathyroidism generally from
Low blood calcium (for any reason) so PTH secretion increases to compensate
Describe renal secondary hyperparathyroidism
Low blood calcium due to kidney disease with insufficient renal production of calcitriol (active form of Vit D)
Describe nutritional hyperparathyroidism, what are the signs
Inadequate calcium in the diet (fed mostly grain or meat)
Signs: due to excessive calcium resorption from bones (osteoporosis) including:
Rubber jaw, skeletal pain, pathological factors, limb deformities (rickets) if animal is growing, lameness, reluctance to move)
What is the objective of a synchronization program in cattle
To manipulate the estrous cycle of normally cycling females so that a large percentage will exhibit estrus with normal fertility at a predetermined time
Why does synchronization often go in hand with artificial insemination
To enhance genetic contribution using desirable steers
Or used to further enhance breeding/calving dates
Why are synchronization programs most successful with heifers
Due to lack of interference from extraneous factors
What are some factors that complicate or prolong synchronization processes
Lactation and the suckling stimulus prolong the postpartum period to first estrus
What are the 4 common hormones used in synchronization programs
Prostaglandins
Estrogens
Progestogens
Gonadotropin releasing hormone
What do prostaglandins do to aid synchronization
Causes regression of the corpus luteum (abortion) (F2-alpha) and allows the cow to return to heat
What do estrogens do to aid synchronization
Stop FSH production
What do progestogens do to aid synchronization
Given as a controlled internal drug release (CIDR) intravaginally to slowly release progesterone (or given by feeding) to suppress ovulation and estrus (follicles can still develop)
Puts the body in the progesterone phase
What do gonadotropin releasing hormone do to aid synchronization
Stimulates the release of FSH and LH, and stimulates follicle maturation and ovulation
