Pharmacology: Endocrine System and Medications

Endocrine System Definition: A network of glands that release hormones into the bloodstream to regulate various functions in the body.

Hypothalamus: Connects the endocrine system to the nervous system.
Pituitary Gland: Often referred to as the "master gland"; regulates various hormone-producing glands.
Thyroid Gland: Produces thyroxine and triiodothyronine, regulating metabolism, growth, and development.
Pancreas: Produces insulin and glucagon to regulate blood sugar.
Ovaries: Produce eggs and hormones like estrogen and progesterone, regulating the menstrual cycle and secondary sexual characteristics.
Testes: Produce sperm and hormones like testosterone, regulating male sexual development and muscle growth.
Parathyroid Glands: Produce parathyroid hormone to control blood calcium levels.
Adrenal Glands: Produce hormones like cortisol, adrenaline, and noradrenaline.

Growth and Development: Controlled by growth hormone from the pituitary.
Metabolism: Regulated by thyroid hormones.
Reproduction: Regulated by sex hormones (estrogen, progesterone, testosterone).
Homeostasis: Regulated by hormones like insulin and antidiuretic hormone (ADH).
Stress Response: Managed by cortisol and adrenaline.

Hormone Synthesis: Hormones are synthesized from cholesterol via enzymatic processes, starting with corticotropin-releasing hormone (CRH) from the hypothalamus leading to ACTH from the pituitary which stimulates the adrenal glands.
Cortisol: Produced during stress and regulates glucose synthesis, protein metabolism, and immune responses.
- Functions:
- Increases gluconeogenesis (synthesis of new glucose).
- Increases proteolysis (breakdown of protein).
- Promotes lipolysis (breakdown of fat).
- Increases blood pressure and dampens inflammatory responses.

Symptoms:
- Round, red face.
- Fat accumulation in the neck (hump).
- Weight gain, hypertension, high blood sugar, fatigue.
Causes: Can result from excessive corticosteroids or benign pituitary adenoma leading to excess ACTH.

Example: Ketoconazole - inhibits various enzymes in the synthesis pathway of cortisol, used for Cushing's syndrome.
- Side Effects: Nausea, vomiting, hepatotoxicity, teratogenic effects.

Aldosterone: Crucial for regulating blood pressure, body fluid balance, and electrolyte levels.
- Mechanism: Promotes sodium reabsorption and potassium excretion in kidneys.
- Pathological Conditions: Addison’s disease requires mineralocorticoid-receptor agonists for treatment.

Fludrocortisone: A synthetic mineralocorticoid that mimics aldosterone, increasing sodium and fluid retention in the body, but can lead to hypokalemia.
Mineralocorticoid Antagonists: Used to oppose aldosterone’s action, leading to sodium loss and lower blood pressure, examples include eplerenone and spironolactone.
- Spironolactone Side Effects: Can cause infertility, hyperkalemia.

Definition: A condition characterized by insufficient thyroid hormone production, impacting metabolism, growth, and development.
Causes: Autoimmune diseases (e.g., Hashimoto's thyroiditis), iodine deficiency, and certain medications.

Primary: Thyroid gland fails to produce sufficient hormones.
Secondary: Insufficient TSH production from the pituitary.
Tertiary: Lack of TRH from the hypothalamus.
Congenital: Inadequate hormone production from birth, leading to developmental delays.

Hormone Replacement Therapies:
- Levothyroxine: Preferred for long-term treatment.
- Liothyronine: Stronger but short-acting option.

Definition: Excessive levels of thyroid hormones leading to increased metabolic rate.
Common Causes:
- Graves' Disease
- Toxic Nodular Goiter

Methimazole: Inhibits thyroid hormone synthesis; first-line treatment.
Radioactive iodine therapy: Permanently damages the thyroid and necessitates hormone replacement post-treatment.