Hormones Flashcards
What is the Endocrine System?
The Endocrine system facilitates the regulation and communication of the body through chemicals called hormones.
Endocrine glands secrete hormones, which travel through the body fluids such as the blood and act on specific target cells in various parts of the body to change their function
How does an Endocrine Gland deliver its hormones to its target cell?
Endocrine glands have no ducts, so they release hormones directly into the bloodstream where they are delivered to their target destination
What are the three main types of hormones?
- Steroids hormones
- Polypeptide hormones
- Amine Hormones
What is a steroid hormone?
- NB: Synthesized from Cholesterol (Common Test Question)
- Examples:
- Estrogen
- Androgens (Such as Testosterone)
- Progesterone
- Cortisol
- Cortisone
- Aldosterone
- They are lipid soluble, so they can travel through the cell membrane to bind to receptors. (may be nuclear receptors depending on the steroid)
What is a Polypeptide hormone?
- Composed of Amino Acids. (Contain C, H, O, N, S)
- Examples:
- Insulin
- Amino Acids can be aromatic, acidic, basic, polar, or nonpolar depending on the R group.
- Can be H20 or Lipid soluble depending on the R group
How do you calculate the mass of an amino acid residue?
110 D is the average weight of a single amino acid in all the naturally occurring amino acid residues based on their frequency.
Remember that H20 is lost in the formation of a peptide bond, this is taken into account in the averaging.
Take 110 D * the number of amino acids in the residue to get the approximate weight of the polypeptide.
Describe the hormone’s journey to the cell
The hormone is secreted from the endocrine gland into the blood stream.
The hormone travels through the blood to its target site
The hormone either binds to a receptor on the cell membrane if it’s H20 soluble, or it passes through the cell membrane and binds to a receptor within the cell either in the cytoplasm or the nucleus.
The hormone likely enters the nucleus regardless of solubility
In the nucleus, activation of mRNA synthesis occurs.
mRNA then goes into the cytoplasm to make proteins.
The whole receptor process is often called a biological cascade. This refers to a series of chemical reactions that occur from the binding of a hormone to a receptor.
Where do H20 soluble hormones bind on their target cell? What types of hormones are H20 soluble?
They bind to a receptor on the cell membrane and then are often brought into the nucleus.
Amine Hormones and some polypeptide hormones are H20 soluble
Where do lipid soluble hormones bind on their target cell? What types of hormones are lipid soluble?
Lipid soluble hormones pass through the cell membrane and bind to a receptor within the cytoplasm or within the nucleus. Most end up in the nucleus regardless of where they bind.
All Steroid hormones are lipid soluble, and some poplypeptide hormones (hydrophobic)
What is an Amine Hormone?
- Amine Hormones are called Catecholamines
- They are made from the amino acid tyrosine.
- They are H20 soluble
- A catechol is a benzene ring with two hydroxy groups on it.
- Examples:
- Dopamine
- Epinephrine (adrenaline)
- Norepinephrine (noradrenaline)
Describe the hypothalamus and what non-tropic hormones it makes?
- The Hypothalamus is the link between the nervous system and the endocrine system
- It’s located in the brain
- Makes:
- Oxytocin
- ADH (vasopressin)
- These two hormones travel along special axons to be stored in the posterior pituitary gland, and will be released from here.
What is Oxytocin?
Oxytocin is a hormone created in the hypothalamus and stored in the posterior pituitary gland.
Oxytocin stimulates milk secretion and stimulates contractions in the uterus. It also stimulates feelings of emotional connection.
What is ADH?
ADH (vasopressin) is a hormone created in the hypothalamus and stored in the posterior pituitary
It is an antidiuretic hormone. It is involved with H20 retention in the kidneys. This hormone helps maintain blood volume by retaining water if there is blood loss.
Describe the positive feedback loop of oxytocin
The more a baby sucks milk from the mammary glands, the more oxytocin is released to stimulate milk secretion.
What are tropic hormones?
Tropic hormones are hormones that stimulate other endocrine glands to release their hormones.
What are the hormones released from the Anterior Pituitary Gland?
Tropic Hormones
- Growth Hormone (Somatotropin)
- FSH (Follicle Stimulating Hormone)
- LH (Leuteinizing Hormone)
- TSH (Thyroid Stimulating Hormone)
- ACTH (Adrenocorticotropic Hormone)
Non-Tropic Hormones
- Prolactin
- MSH (Melanocyte-Stimulating Hormone)
What is the function of Growth Hormone?
- It is a tropic hormone released from the anterior pituitary
- Also known as somatotropin
- Growth Hormone is involved with stimulation of bone growth.
- Increases DNA, RNA, and protein synthesis
- Stimulates the liver to release IGFs (Insulin growth factors) which allow for bone and cartilage growth
- Increases blood sugar
- Abnormal amounts can result in hypersecretion (giantism) or hyposecretion (dwarfism)
- If done before puberty Growth hormone therapy can be used to treat dwarfism
What is the function of FSH?
Follicle Stimulating Hormone
- It is a tropic hormone released from the anterior pituitary
- Ovarian follicle in women
- Spermatogenesis in men
What is the function of LH?
Luteinizing hormone
- It is a tropic hormone released from the anterior pituitary
- Stimulates ovulation
- progesterone secretion
- corpus luteum formation in women in the ovary,
- stimulates testosterone secretion in men
What is the corpus luteum
- The corpus luteum is a mass of cells that forms in the ovary during the menstruation cycle.
- The mass of cells is an endocrine gland that secretes progesterone.
- The Progesterone induces changes in the uterus that makes it suitable for the implanting of an embryo
What is the function of TSH?
Thyroid Stimulating Hormone
- It is a tropic hormone released from the anterior pituitary
- Will stimulate the thyroid gland to make and release hormones
What is the function of ACTH?
Adrenocorticotropic Hormone
- It is a tropic hormone released from the anterior pituitary
- Will stimulate the adrenal cortex to secrete glucocorticoids (steroid hormones) such as cortisol
What is the adrenal cortex?
- The adrenal cortex is the outer portion of the adrenal gland.
- The adrenal gland is located on top of the kidneys
What is prolactin?
- Prolactin is a non-tropic hormone released from the anterior pituitary gland
- Stimulates mammary gland growth and milk production in mammals
- Has cytokine-like functions involved in the immune system
- Acts as a growth factor
- In fish, it controls water and salt balance
What is MSH?
Melanocyte Stimulating Hormone is a non-tropic hormone released from the anterior pituitary gland
- Regulates the function of melanocytes, involved with skin, hair, eyes, etc.
- Pigmentation in humans, reptiles, amphibians, and fish
- Can suppress appetite in humans by binding to receptors in the hypothalamus
What is Leptin?
Leptin is a hormone made by adipose cells that acts in appetite suppression
What is the thyroid gland?
- The thyroid gland has two lobes on the ventral side of the trachea
- produces thyroid hormone, which is really two hormones
- T3 (Triiodothyronine) - has 3 iodine atoms
- T4 (Thyroxine) - has 4 iodine atoms
What are T3 and T4?
- T3 (triiodothyronine) and T4 (thyroxine) are thyroid hormones.
- They bind to the same receptor
- T4 is more abundant
- These hormones are involved in
- Growth,
- Cell Differentiation,
- Control of O2 Consumption
- Basal Metabolic Rate
What is hyperthoyroidism?
Hyperthyroidism is too much T3 and T4 production. It results in:
- increase in metabolism
- weight loss
- profuse sweating
- high blood pressure
- irritability
Graves disease is the most common form of hyperthyroidism
What is Graves disease?
Graves disease is the most common form of hyperthyroidism.
It’s an autoimmune disease that often has patient’s eyes protruding
What is hypothyroidism?
Hypothyroidism is too little T3 and T4 hormone Results in: - Feeling cold - Gaining weight - Feeling tired all the time
The body tries to compensate for this by increasing TSH from the anterior pituitary gland. It attempts to entice the thyroid to make more thyroid hormone. This is not good. Constant TSH causes the thyroid to enlarge creating a goiter.
What is Myxedema
Myxedema is a severe case of hypothyroidism
In myxedema we see swelling of the face, lips, eyelids, and even tongue. Heart rate and blood pressure are often quite low.
What is Cretinism?
Cretinism is an extreme form of hypothyroidism in fetal life through adulthood.
Mental retardation and growth failure are noted
What is Hashimoto’s disease?
Hashimoto’s disease is an autoimmune disease.
- It is the most common cause of hypothyroidism.
- It is most prevalent in middle-aged women
- Untreated Hashimotos can result in:
- Myxedema
- Heart Problems
- Goiter
- Depression
What is Calcitonin?
Calcitonin is a thyroid hormone that “tones down” or lowers blood calcium.
- Ca++ reabsorption by the kidneys is lessened
- inhibits osteoclast activity and promotes bone formation by osteoblasts, decreasing Ca++ levels as bones are formed.
What is the parathyroid gland?
The parathyroid gland is four lobes located on the posterior of the thyroid.
- It secretes PTH (parathyroid hormone)
What is PTH?
Parathyroid Hormone is secreted from the parathyroid
It causes:
- an increase in blood calcium concentration
It influences 3 organ types:
- Bone: Indirectly causes Osteoclast activity to increase and Osteoblast activity to decrease
- Kidney: reabsorption of Ca++ increases. Some kidney cells release an enzyme that allows Vitamin D to be activated
- Intestine: The intestine uses the activated Vitamin D to absorb Ca++ from food.
What happens if you don’t have enough Vitamin D?
Without enough Vitamin D, the body is not allowed to absorb enough calcium or phosphorus, thus bone development is retarded.
In children the pathology is called rickets
