Endocrine Lecture 1 - Intro to Endocrine

The endocrine system consists of glands that produce and secrete hormones.
The main functions involve regulating metabolism, growth, development, reproduction, and emotional responses.
Key glands include the pituitary, thyroid, parathyroid, adrenal, pancreas, ovaries, testes, thymus, and pineal gland.

Gland: A group of cells that produce and secrete hormones, enzymes, and other substances.
Exocrine Gland: Secretes substances through ducts to outside or into the body (e.g., digestive enzymes).
Endocrine Gland: Releases hormones directly into the bloodstream (e.g., hormones regulating metabolism).
Hormonal changes can disrupt the body's metabolic balance.

Hormones travel through the bloodstream to target organs.
Involved in various bodily functions including:
- Metabolism
- Growth and development
- Reproduction
- Temperature regulation
- Fluid balance
- Emotional responses
Negative Feedback System: Homeostatic mechanism where a primary hormone prompts the release of a second hormone which inhibits the first.

Known as the "master gland"; controls other endocrine glands.
Located beneath the hypothalamus; divided into anterior and posterior sections.
Anterior Pituitary Hormones:
- Somatotropin (Growth Hormone)
- Adrenocorticotropic Hormone (ACTH)
- Thyroid-stimulating Hormone (TSH)
- Follicle-stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
- Prolactin (stimulates milk production).
Posterior Pituitary Hormones:
- Oxytocin (stimulates milk release and uterine contractions)
- Antidiuretic Hormone (ADH or vasopressin, regulates water retention in kidneys).

Butterfly-shaped gland located on either side of the trachea.
Highly vascular, receiving significant blood flow.
Major hormones include:
- Triiodothyronine (T3) and Thyroxine (T4): Regulate metabolism and nervous system activity.
- Calcitonin: Decreases blood calcium levels by promoting calcium storage in bones.

Four glands located on the back surface of the thyroid.
Secretes Parathyroid Hormone (PTH), which increases blood calcium levels and regulates phosphorus levels.
Understand the balance needed between calcitonin and PTH to regulate calcium levels in the body.
Hypocalcemia (low calcium) can cause muscle spasms and arrhythmias; Hypercalcemia (high calcium) can impair heart function.

Located on top of each kidney, consisting of two parts:
Adrenal Cortex:
- Mineralocorticoids (e.g., aldosterone) regulate sodium and potassium levels and water balance.
- Glucocorticoids (e.g., cortisol) are involved in glucose metabolism and stress response.
- Sex Hormones: Androgens (e.g., testosterone, estrogen) important for sexual development.
Adrenal Medulla: Secretes epinephrine and norepinephrine, activating the body's 'fight or flight' response (increased heart rate, blood pressure, and energy availability).

Elongated gland posterior to the stomach; includes endocrine and exocrine functions.
Islets of Langerhans: clusters of cells that secrete insulin and glucagon.
Insulin: Lowers blood glucose levels, secreted by beta cells in response to high glucose.
Glucagon: Raises blood glucose levels, secreted by alpha cells when glucose is low.

Ovaries produce estrogen and progesterone, necessary for menstrual cycle regulation and pregnancy maintenance.
Placenta: Temporary endocrine gland during pregnancy, releases hormones needed to sustain pregnancy.

Testes: Produce testosterone, necessary for male secondary sex characteristics and sperm production.

Located in the upper thorax, posterior to the sternum.
Produces thymosin, involved in T-lymphocyte development for the immune response.

Small, cone-shaped gland in the brain; secretes melatonin, which regulates sleep patterns and circadian rhythms.

This overview presents the key concepts of the endocrine system; further details will be explored in following discussions.