Endocrinology

Hopefully made easy!

Introduction/General Info

Endocrine glands- secrete hormones. Exocrine glands- produce secretions that

are released via ducts. Hormones- chemical messengers carried

by plasma. Regulates the activity of the target

organ. Not all hormones are secreted by

endocrine glands, some are produced in tissue from another organ. Like EPO – produced by kidney

Introduction/General Info

Major Endocrine Glands- Pituitary Thyroid glands Parathyroids Pancreas Ovaries Testes Adrenal glands

The Pituitary Gland

Pituitary Gland

Divided into 2 lobes, each of which acts as a separate gland. Anterior Posterior

Mainly influenced by the Hypothalamus.

Anterior Pituitary Gland

“Master Endocrine Gland” Develops from glandular tissue.

Hormones-1. Growth Hormone (GH)-

Promotes body growth Regulates metabolism Encourages protein synthesis

Anterior Pituitary Gland…

2. Prolactin (PRL)- Triggers and maintains lactation.

3. Thyroid-stimulating Hormone (TSH)- Stimulates the growth and

development of the thyroid gland.4. Adrenocorticotropic Hormone (ACTH)-

Stimulates the growth and development of the adrenal cortex

Anterior Pituitary Gland…

5. Follicle-stimulating Hormone (FSH)- Stimulates the growth &

development of the ovarian follicles.

Stimulates the follicle lining to produce & secrete ESTROGEN.

Stimulates spermatogenesis.

Anterior Pituitary Gland…

6. Luteinizing Hormone (LH)- Completes the follicle development

process. Can cause OVULATION. Can cause the development of the

CORPUS LUTEUM- Which produces PROGESTERONE, which maintains pregnancy.

Can stimulate the testes to develop & produce TESTOSTERONE.

Posterior Pituitary Gland

Develops from the nervous system.

Does not produce any hormones.

Stores ADH & Oxytocin

Posterior Pituitary Gland…

1. Antidiuretic Hormone (ADH)- Prevents diuresis-

Conserves water Urine is more concentrated

The release of ADH is inhibited by alcohol and caffeine.

Posterior Pituitary Gland…

2. Oxytocin- Has 2 targets-

The uterus & mammary glands Can cause uterine contractions to:

Aid in the transport of sperm to the oviducts.

Aid in the delivery of the fetus.

The Thyroid Gland

The Thyroid Gland

Produces: Thyroid hormones

T3- has 3 iodine atoms

T4- has 4 iodine atoms Calcitonin

Parathyroid Glands

Produces parathyroid hormone (PTH)

Works opposite to calcitonin to maintain blood calcium levels.

Mobilizes calcium from bones to the bloodstream. Negative feedback loop.

The Adrenal Glands

The Adrenal Glands…

Actually 2 glands- Adrenal

cortex Adrenal

medulla

The Adrenal Glands…

Adrenal Cortex- Develops from glandular tissue. Under the influence of ACTH, it

produces steroids: Glucocorticoids Mineralocorticoids Sex hormones

Chemicals derived from cholesterol.

The Adrenal Glands…

Adrenal Cortex…1. Glucocorticoids-

Cortisone, Cortisol, & Corticosteronea. Cortisol- aka hydrocortisone,

influences the metabolism of sugars and has a anti-inflammatory effect.

b. Cortisone- similar to Cortisol, and can be prepared synthetically. Useful in treating inflammatory conditions.

Causes a hyperglycemic effect. Causes blood glucose levels to rise.

The Adrenal Glands… Adrenal Cortex…2. Mineralocorticoids-

Regulates electrolyte levels. The primary one is ALDOSTERONE.

Reabsorbs sodium, excretes potassium.

3. Sex Hormones- Androgens- male Estrogens- female

Maintain secondary sex characteristics (beard & breast development)

These hormones are also produced in the ovaries & testes.

The Adrenal Glands… Adrenal Medulla-

Develops from nervous tissue. Produces (catecholamines):

Epinepherine Norepinepherine

Chemicals derived from amino acids Along with the sympathetic nervous

system, these catecholamines stimulate the “Fight or Flight” response.

The Adrenal Glands… Adrenal Medulla…1. Epinepherine-

heart rate, dilates bronchioles, and stimulates the production of glucose for energy.

2. Norepinepherine- Constricts blood vessels and

raises blood pressure.

The Pancreas

The Pancreas…

Controls metabolism Secretes:

1. Somatostatin- inhibits the secretion of insulin & glucagon.

2. Insulin- glucose 3. Glucagon- glucose

Pathology

Hyperthyroidism

The most commonly seen endocrine disorder in cats.

Very rare in dogs except as a result of neoplasia.

Bilateral thyroid gland enlargement occurs in 70% of cases.

Hyperthyroidism…

Signs include: Weight loss Polyphagia Vomiting Increased appetite Tachycardia (with or without

murmurs)

Hyperthyroidism…

Treatment options include: Surgical removal of the

thyroid gland Radioactive iodine treatment Antithyroid drug therapy

Hypothyroidism Commonly seen in the dog. Clinical signs include:

Weight gain with no change in diet.

Bilateral symmetric alopecia & loss of hair on the tail (“rat tail”).

66-75% of dogs will have an increased cholesterol level.

Parathyroid Hyperparathyroidism-

production of parathormone. Causes hypercalcemia. Etiology is often a parathyroid tumor.

Hypoparathyroidism- production of parathormone. Causes hypocalcemia.

This leads to a condition called tetany- Constant muscle contraction.

Adrenal Cortex

Hyperadrenocorticoidism- “Cushing’s Disease” Produced by excess cortisol

from the adrenal cortex. Hypoadrenocorticoidism-

“Addison’s Disease” Hypofunctioning of the adrenal

cortex.

Pancreas

Hyperinsulinism- Excess secretion of insulin

causing hypoglycemia. A problem of ferrets. Etiology may be a pancreatic

tumor or an overdose of insulin.

Pancreas Diabetes mellitus-

Lack of insulin secretion or resistance of insulin to promote sugar, starch, and fat metabolism in cells.

Symptoms include: PU/PD, glucosuria, and +/- ketoacidosis. Ketoacidosis- fats are improperly burned leading to an accumulation of ketones in the body.

Pancreas Type I Diabetes-

Insulin-dependant diabetes mellitus (IDDM) Onset is usually in young animals. A complete deficiency of insulin. Patients require injections of insulin for

treatment. Type II Diabetes-

Non-insulin-dependant diabetes mellitus (NIDDM)

A separate disease from type I. Still has a deficiency of insulin. Usually in older, obese animals. Treatment is with diet and oral medications.

Laboratory Analysis

Lab Analysis…

Glucose tolerance Thyroid tests- T3, T4, Free T4,

TSH ACTH Stim. Dexamethasone Suppression-

LDDS HDDS

Urine Cortisol : Creatinine

THE END!