The Endocrine System & Steroid Hormones

Endocrine system

• a system composed of ductless glands that release hormones into the bloodstream that affect a target organ and regulate growth, metabolism, or reproduction

8 major endocrine glands

• Pineal

• Pituitary

• Thyroid

• Thymus

• Adrenal 

• Pancreas

• Ovary

• Testes

Hypothalamus

Releasing and inhibiting hormones

Pituitary Gland (“master gland”)

Anterior pituitary (adenohypophysis)
Tropic hormones- hormones that are released from the adenohypophysis

Posterior pituitary (neurohypophysis)

Anterior Pituitary Hormones

• Adrenocorticotropic Hormone (ACTH)

  • Starts cortisol production

• Thyroid stimulating hormone (TSH)

• Follicle stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Prolactin

• Growth hormone (GH)

Posterior Pituitary Hormones
Oxytocin

• Labor

• Stimulates milk production from mammary glands

• Decreases postpartum bleeding

Posterior Pituitary Hormone
Antidiuretic hormone (ADH)

• Insufficient ADH = diabetes insipidus

  • Hormone replacement with vasopressin (DDAVP®)

Adrenal cortex secretes two types of steroid hormones

Glucocorticoids
Cortisol 

Mineralocorticoids 

Aldosterone 

Factors that stimulate the hypothalamus to release CRH

• Stress, anxiety

• Exercise

• Cold weather

• Infection

• Injury, surgery

Glucocorticoids Functions

Regulate the metabolism of carbohydrates, proteins, and fats particularly during stress

Gluconeogenesis

• Lipolysis

• Inhibit glucose uptake by the cells

Glucocorticoids Anti-inflammatory effect

Works at the lipase site

Synthetic Glucocorticoids Short-acting
(12-24 hours)

hydrocortisone (Cortef®, Cortaid®)

Synthetic Glucocorticoids
Intermediate-acting (24-36 hours)

• methylprednisolone (Medrol®)

• prednisolone (Prelone®)

• prednisone 

• triamcinolone (Aristocort® and Kenalog®) *36-48 hours

Synthetic Glucocorticoids
Long-acting (48-72 hours)

• betamethasone (Celestone®)

• dexamethasone (Decadron®)

Side Effects of Glucocorticoids
Common

• Increase in appetite

• Weight gain

• Indigestion/GI upset

• Restlessness

• Hirsutism 

• Poor wound healing

• Increased risk for infection

• Osteoporosis

• Muscle wasting

Side Effects of Glucocorticoids
less frequent

• Change in skin color

• Dizziness

• Increased sweating

• Flushing of the face

• Skin rash

Mineralocorticoids 

• Used to maintain water balance

• Aldosterone 

• Synthetic mineralocorticoid:

  • fludrocortisone (Florinef®)

Side Effects of Mineralocorticoids

• Edema

• Hypertension

• Arrhythmias

• Muscle weakness

Addison’s Disease

Primary adrenal insufficiency 

Addison’s Disease Symptoms

• Dehydration

• Hypotension

• Muscle weakness 

Treatment: chronic hormone replacement therapy

• Glucocorticoids

• Mineralocorticoids

Cushing’s Syndrome

Excessive glucocorticoid production

Cushing’s Syndrome
Symptoms

• Weight gain

• Edema

• Thinning of skin

• Hyperglycemia

Cushing’s Syndrome
Treatment

adrenalectomy