Hormones

• Erythropoietin is released by the kidney to stimulate red blood cell production in bone marrow in response to hypoxia.
• Renin is an enzyme released by the kidney to convert angiotensin.
• GHRH in the lungs influences cell proliferation, metabolism, and inflammation locally.
• Atrial Natriuretic Peptide (ANP) is produced by cells in the heart's atria in response to stretching of the atrial walls from elevated blood volume and pressure.
• ANP causes excretion of sodium and water by the kidneys, vasodilation, and inhibits renin and aldosterone release.
• Relaxin is released by the placenta to relax ligaments in the pelvis, particularly the pubic symphysis.
• This widening of the pelvic outlet facilitates the passage of the baby through the birth canal during delivery and softens/ripens the cervix.
• Human chorionic gonadotropin (hCG), a pregnancy hormone, is produced by the trophoblastic cells (syncytiotrophoblastic cells) of the placenta during pregnancy.
• It can be detected in urine or blood, so it is used in pregnancy tests.
• The Renin-Angiotensin-Aldosterone System (RAAS) regulates blood pressure and fluid balance by controlling sodium and water retention.
• Bony fish (teleosts) have a urophysis, which is a neuroendocrine gland in the tail area that is a specialized region of the spinal cord's caudal end.
• Corpuscles of Stannius are unique endocrine glands in the kidneys of bony fish (teleosts) and lower blood calcium levels.
• Ultimobranchial tissue is found in non-mammalian vertebrates like fish, amphibians, reptiles, and birds, and plays a crucial role in calcium regulation.
• Chromaffin tissue is located around the adrenal gland in mammals, but in fish, it's near the esophagus, and in other non-mammalian vertebrates, near the thyroid gland.
• Insects have an open circulatory system with hemolymph.
• Insects and other arthropods, like crustaceans, have unique glands.
• Gonad-stimulating substance (GSS), a neuropeptide, is a key regulator of gamete shedding and oocyte maturation in sea stars (echinoderms).
• Echinoderms lack a centralized circulatory system but have mechanisms for circulating coelomic fluid, which may help distribute hormones.
• Pyloric caeca are the main digestive glands in echinoderms, secreting digestive enzymes and absorbing nutrients.
• Radial canals in echinoderms are closely associated with the radial nerve, allowing neurohormones from the nerve to diffuse into the fluid of the radial canals.

Diseases

• Polycystic Ovarian Syndrome (PCOS) involves ovaries containing multiple small, immature follicles resembling cysts, which hormonal imbalances prevent from maturing or releasing eggs (anovulation).
• In Gigantism, overproduction of GH due to a benign tumor (pituitary adenoma) on the pituitary gland causes abnormal stimulation of bone and tissue growth.
• In Acromegaly, overproduction of GH leads to excess IGF-1 (Insulin-like Growth Factor 1) from the liver, causing tissue overgrowth.
• Hyperthyroidism is when the thyroid gland is overactive and produces too much T3 and T4, speeding up body functions; a common cause is Graves’ Disease, an autoimmune condition that stimulates the thyroid uncontrollably.
• Hypothyroidism is caused by Hashimoto’s disease (immune system attacks the thyroid), iodine deficiency, or pituitary dysfunction, resulting in the body slowing down due to not enough thyroid hormone (T3 and T4).

Glands, Hormones, and Target Tissues

• Anterior Pituitary:
• Growth hormone targets most tissues and increases gene expression, breakdown of lipids, release of fatty acids, and glucose levels.
• Thyroid-stimulating hormone targets the thyroid gland and increases thyroid hormone secretion (thyroid and triiodothyronine).
• Adrenocorticotropic hormone (ACTH) targets the adrenal cortex and increases secretion of glucocorticoid hormones such as cortisol, increasing skin pigmentation at high concentrations.
• Melanocyte-stimulating hormone (MSH) targets melanocytes in skin and increases melanin production, darkening skin.
• Luteinizing hormone (LH) promotes ovulation and progesterone production in the ovary, and testosterone synthesis and sperm cell production support in the testis.
• Follicle-stimulating hormone (FSH) promotes follicle maturation and estrogen secretion in the ovary, and sperm cell production in the testis.
• Posterior Pituitary:
• Antidiuretic hormone (ADH) targets the kidney, and conserves water and constricts blood vessels.
• Oxytocin targets the uterus and mammary gland, increases uterine contractions, and increases milk letdown from mammary glands.
• Thyroid Gland:
• Thyroid hormones (thyroxine, triiodothyronine) target most cells of the body and increases metabolic rates, essential for normal growth and maturation.
• Calcitonin primarily targets bone, decreases the rate of bone breakdown, and prevents large increases in blood calcium levels.
• Parathyroid Glands:
• Parathyroid hormone targets bone and kidney, increases the rate of bone breakdown by osteoclasts, and increases vitamin D synthesis.
• Adrenal Medulla:
• Epinephrine (mostly) and some norepinephrine target the heart, blood vessels, liver, and adipocytes, increasing cardiac output, blood flow to skeletal muscles and heart, and glucose and fatty acids into the blood.
• Adrenal Cortex:
• Mineralocorticoids (aldosterone) target the kidneys, intestine, and sweat glands, increasing the rate of sodium transport into the body and potassium secretions, secondarily favoring water retention.
• Glucocorticoids (cortisol) target most tissues, increasing lipid and protein breakdown, glucose synthesis from amino acids, blood nutrient levels, and inhibiting inflammation and immune response.
• Adrenal androgens target most tissues; they are insignificant in males but increase female sexual drive and growth of pubic and axillary hair.
• Pancreas:
• Insulin (beta cells) targets the liver, skeletal muscle, and adipose tissue, increasing the uptake and use of glucose and amino acids.
• Glucagon (alpha cells) primarily targets the liver, increasing the breakdown of glycogen and the release of glucose into the circulatory system.
• Somatostatin (delta cells) target the gastrointestinal tract and pancreas, inhibiting insulin and glucagon.
• Reproductive Organs:
• Testes (Testosterone) targets most tissues and aids in sperm cell production, maintenance of functional reproductive organs, secondary sex characteristics, and sexual behavior.
• Ovaries (Estrogens, Progesterone) target most tissues and aid in uterine and mammary gland development and function, external genitalia structure, secondary sex characteristics, sexual behavior, and menstrual cycle.
• Uterus, Ovaries, and Inflamed Tissues:
• Prostaglandins target most tissues, mediating inflammatory responses, increasing uterine contractions, and ovulation.
• Thymus:
• Thymosin targets immune tissues, promoting immune system development and function.
• Pineal Gland:
• Melatonin targets the hypothalamus and inhibits the secretion of gonadotropin-releasing hormone, inhibiting reproduction.