Chapter 14 - Endocrinology

glucose

A simple sugar in foods and also the sugar in the blood (produced when the hormones glucagon or cortisol break down stored glycogen)

glycogen

Glucose stored in the liver and skeletal muscles. Glycogen is broken down into glucose by the hormone glucagon from the pancreas and by the hormone cortisol from the adrenal cortex.

norepinephrine

Hormone secreted by the adrenal medulla.

endocrine system

Body system that includes glands that produce and secrete hormones into the blood. These glands include the hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus, pancreas, adrenal glands, ovaries, and testes. The endocrine system is also known as the neuroendocrine system because of the connection between it and the nervous system.

testosterone

Male sex hormone that is the most abundant and biologically active of the androgens. Testosterone is secreted by the interstitial cells of the testes when stimulated by LH from the anterior pituitary gland.

gonadotropins

Category of hormones that stimulates the male and female sex glands (gonads). It includes FSH and LH.

pineal gland

Endocrine gland between the two lobes of the thalamus. It secretes the hormone melatonin. It is also known as the pineal body.

pituitary gland

Endocrine gland in the brain that is connected by a stalk of tissue to the hypothalamus. It sits in the bony cup of the sella turcica of the spheroid bone. It is also known as the hypophysis. It is the master gland of the body. It consists of two separate glands: the anterior pituitary gland and the posterior pituitary gland.

thyroid gland

Endocrine gland in the neck that secretes the hormones T3, T4, and calcitonin. Its two lobes have a shield-like shape with a band of tissue across the trachea.

thymus

Endocrine gland posterior to the sternum and within the mediastinum. It secretes a group of hormones known as thymosins. They cause immature T lymphocytes in the thymus to mature.

hypothalamus

Endocrine gland within the brain just below the thalamus. The hypothalamus secretes hormones that stimulate or inhibit the secretion of hormones from the anterior pituitary gland. It also produces antidiuretic hormone (ADH) and oxytocin. These two hormones are stored in the posterior pituitary gland.

adrenal glands

Endocrine glands on top of the kidneys. An adrenal gland contains a cortex and a medulla, each of which is a gland that secretes its own hormones.

progesterone

Female sex hormone secreted by the corpus luteum of the ovary when stimulated by LH from the anterior pituitary gland.

parathyroid glands

Four endocrine glands on the posterior surface of the thyroid gland. They secrete parathyroid hormone.

mineralocorticoids

Group of hormones secreted by the adrenal cortex. See aldosterone.

T3

Hormone secreted by the throid gland. It increases the rate of cell metabolism. It is also known as triiodothyronine.

calcitonin

Hormone secreted by the thyroid gland. It regulates the amount of calcium in the blood. If the calcium level is too high, calcitonin moves calcium from the blood and deposits it in the bones.

gland

Structure of the endocrine system that produces and secretes one or more hormones into the blood.

Ovaries

Endorcrine glands near the uterusl there are also the female sex glands (gonads). FSH from the anterior pituitary gland stimulates the follicles of the ovary to secrete estradiol. LH from the anterior pituitary gland stimulates the corpus luteum (ruptered follicle) to secrete etradiol and progesterone. Th e cells around the follicles secrete the male sex hormone testosterone.

estrogens

Female sex hormones, such as estradiol from the ovaries. In the blood, androgens from the adrenal cortex are changed into estrogens.

glucocorticoids

Group of hormones secreted by the adrenal cortex. See cortisol.

insulin

Hormone secreted by beta cells in the islets of Langerhans. It transports glucose into the cells where it is metabolized for energy.

somatostatin

Hormone secreted by delta cells in the islets of Langerhans. It prevents the hormones glucagon and insulin from being secreted by the pancreas. It prevents growth hormone from being secreted by the anterior pituitary gland.

epinephirne

Hormone secreted by the arenal medulla in response to a nerve impulse from the sympathetic division of the nervous system. It produces the "fight-or-flight" response.

parathyroid hormone

Hormone secreted by the parathyroid glands. It regulates the amount of calcium in the blood. If the calcium level is too low, parathyroid hormone moves calcium from the bones to the blood.

melatonin

Hormone secreted by the pineal gland. It maintains the 24-hour wake-sleep cycle.

T4

Hormone secreted by the thyroid gland. Most of it is changed into T3 by the liver. It is also known as thyroxine.

androgens

Male sex hormones, such as testosterone from the testes, and other androgens secrted by the adreanl cortex. In the blood, androgens from the adrenal cortex are changed into estrogens.

adrenal medulla

Inner layer of the adrenal gland. It secretes the hormones norepinephrine, epinephrine, and dopamine.

cortisol

Most abundant and biologically active of the glucocorticoid hormones secrted by the adreanl cortex. It breaks down stored glycogen to increase the level of glucose in the blood. It decreases the formation of proteins and new tissues, and it has an anti-nflammatory effect. THe adreanl cortex secrtes cortisol when stimulated by ACTH from the naterior pituitary gland.

aldosterone

Most abundant and biologically active of the mineralcorticoid hormones secreted by the adreanl cortex. The adrenal cortex secretes alduosterone when the blood pressure is low. It moves sodium and water from tubules in the nephrons of the kidney into the blood while allowing potassium to be excreted in the urine. This increases the blood colume and the blood pressure.

adrenal cortex

Outer layer of the adrenal gland. It secretes three groups of hormones: mineralocorticoids (aldosterone), glucocorticoids (cortisol), and androgens (male sex hormones).

anterior pituitary gland

Part of the pituitary gland hat produces and secretes seven hormones: thyroid-stimulating hormone (TSH) follicle-stimulating hormone (FSH), lutenizing hormone (LH_ prolactin, adrenocorticotropic hormone (ACTH), growth hormone (GH), and melanocyte-stimulating hormone (MSH). It is also known as the adenohypophysis.

posterior pituitary gland

Part of the pituitary gland that stores and releases antidiuretic hormone (ADH) and oxytocin produced by the hypothalamus it releases these hormones in response to a nerve imulse from the hypothalamus. It is also known as the neurohypophysis.

homeostasis

State of equilibrium of the internal environment of the body. The endocrine system plays a role in homeostasis by regulating body fluids, electrolytes, glucose, cell metabolism, growth, and the wake-sleep cycle.

euthyroidism

State of normal functioning of the hormones of the thyroid gland.

thyroid-stimulating hormone (TSH)

Hormone produced and secreted by the anterior pituitary gland. It causes the thyroid gland to grow and stimulates it to secrete the thyroid hormones T3 and T4.

pancreas

Endocrine gland posterior to the stomach. It contains the islets of Langerhans (alpha, beta, and delta cells) that secrete the hormones glucagon, insulin, and somatostatin.

Testes

Endocrine glands on either side of the scrotum. They are the male sex glands (gonads). They are also known as testicles. FSH from the anterior pituitary gland stimulates their seminiferous tubules to produce spermatozoa. LH from the anterior pituitary gland stimulates their interstitial cells to secrete testosterone.

Estradoil

Female sex hormone that is the most abundant and biologically active of all the estrogens. Estradiol is secreted by the follicles and corpus luteum of the ovary when stimulated by FSH from the anterior pituitary gland.

luteinizing hormone (LH)

Hormone produced and secreted by the anterior pituitary gland. In females, it stimulates a follicle in the ovary to release a mature ovum. It stimulates the corpus luteum (ruptured ovarian follcile) to secrete estradiol and progesterone. In males, it stimulates the interstitial cells of the testes to secrete testosterone.

follicle-stimulating hormone (FSH)

Hormone produced and secreted by the anterior pituitary gland. In females, it stimulates follicles in the ovary to produce mature ova and to secrete the hormone estradiol. In males, it stimulates the seminiferous tubules of the testes to produce spermatozoa.

melanocytestimulating hormone (MSH)

Hormone produced and secreted by the anterior pituitary gland. It is secreted in pregnant women and stimulates melanocytes in the skin to produce melanin. This causes skin pigmentation on the face and abdomen.

growth hormone (GH)

Hormone produced and secreted by the anterior pituitary gland. It stimulates growth and protein synthesis in all cells. It increases height and weight during childhood and puberty.

adrenocorticotropic hormone (ACTH)

Hormone produced and secreted by the anterior pituitary gland. It stimulates the cortex of the adrenal gland to secrete its hormones.

prolactin

Hormone produced and secreted by the anterior pituitary gland. It stimulates the development of the breasts during puberty and stimulates the mammary glands to release milk for breastfeeding.

antidiuretic hormone (ADH)

Hormone produced by the hypothalamus but stored in and released by the posterior pituitary gland. ADH moves sodium and water from tubules in the nephron of the kidney into the blood. This decreases urine output and keeps the blood volume and blood pressure normal.

oxytocin

Hormone produced by the hypothalamus but stored in and released by the posterior pituitary gland. It stimulates the pregnant uterus to contract during labor and childbirth. It causes the uterus to contract after birth to prevent hemorrhaging. It causes the breasts to release milk for breastfeeding ("let-down reflex") when the baby cries or sucks.

glucagon

Hormone secreted by alpha cells in the islets of Langerhans. It breaks down stored glycogen to increase the glucose in the blood.