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What are chemical compounds secreted into the blood that affect target tissues generally at a site distant from original production?
Name the 3 classes of hormones
What synthesizes steroid hormones?
- Adrenal glands
- Synthesized from cholesterol as needed, not stored, lipid soluble
How are steroids circulated in the blood?
Need a carrier protein to circulate in the blood
Name the clinically significant hormones
How do steroid hormones work?
Free hormone is transported across cell membrane to interact with intracellular receptor
How are steroids regulated?
Negative feedback by another hormone (cortisol/ACTH)
What are protein hormones synthesized by?
- Anterior pituitary
- Parathyroid glands
- Synthesized then stored in the cell as secretory granules until needed
How are protein hormones carried in the blood?
- NO carrier needed
- Water soluble
Name the clinically significant protein hormones
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Thyroid stimulating hormone (TSH)
- Human chorionic gonadotrophin (hCG)
- Parathyroid hormone
- Growth hormone
Name the glycoprotein hormones
What are the glycoproteins (FSH, LH, TSH, and hCG) composed of?
- Alpha chains - identical
- Beta chains - unique for each hormone
How do protein hormones work?
Protein hormones interact with a cell membrane receptor - which activates a second messenger system and then cellular action
How is protein hormone synthesis regulated?
- Change in analyte concentration in serum
- Negative feedback by another hormone
How are amine hormones synthesized?
- Synthesized by thyroid and adrenal glands
- Synthesized from amino acids
How are amine hormones carried in the blood?
Some amine hormones require a carrier protein and others do not
Name the clinically significant amine hormones
- Thyroxine (T4)
- Triiodothyronine (T3)
How do the amine hormones work?
- Epinephrine and norepinephrine do NOT bind to carrier proteins and interact with the receptor site on the cell membrane
- T4 and T3 circulate bound to carrier proteins, with the free hormone being transported across the cell membrane to interact with the intracellular receptor
How are the amine hormones regulated?
- Regulated by nerve stimulation
- Another hormone
- Negative feedback
Name the hormones produced by the hypothalamus
- Corticotropin releasing hormone (CRH)
- Gonadotropin releasing hormone (GnRH)
- Growth hormone releasing hormone (GHRH)
- Thyrotropin releasing hormone (TRH)
What hormone stimulates secretion of adrenocorticotropic hormone (ACTH)?
Corticotropin releasing hormone (CRH)
What hormone stimulates secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH)?
Gonadotropin releasing hormone
What hormone stimulates secretion of thyroid stimulating hormone (TSH) and prolactin?
Thyrotropin releasing hormone (TRH)
What hormone inhibits prolactin release?
What hormone inhibits secretion of TSH and GH?
Where does the antidiuretic hormone get produced?
Supraoptic and paraventricular nuclei of the hypothalamus
What other names is the antidiuretic hormone (ADH) known by?
Name the hormones secreted by the anterior pituitary
What does an increase of cortisol level do?
Increased levels of cortisol turns off secretion of ACTH and CRH
What does a decrease of cortisol level do?
Decreased levels of cortisol stimulates secretion of ACTH through negative feedback - which promote cortisol synthesis
What else is the growth hormone known as?
What effect does the growth hormone have?
- Antagonistic effect to insulin in relationship the glucose metabolism
- Stimulates gluconeogenesis in the liver
- Stimulates lipolysis
- Promotes protein synthesis
What is the reference range for growth hormone?
Basal level 2-5 ng/mL
What is the clinical significance of increased levels of growth hormone?
- Pituitary gigantism
- Acromegaly (enlarged feet, hands, and facial bones...)
What is the clinical significance of decreased levels of growth hormone?
- Adults - caused by pituitary adenomas or irradiation
- Children - may be familial or caused by a tumor, craniopharyngioma; results in pituitary dwarfism
When is prolactin secreted and by what?
- Released upon stimulation from TRH
- Secreted by pituitary lactotroph cells
What inhibits the release of prolactin?
What hormone has the following functions:
-Initiates and maintains lactation
-Effects reproduction through ovarian and testicular steroidogenesis
-Affects the immune system
What is the reference range for prolactin?
- Males: 3.0-14.7 ng/mL
- Females: 3.8-23.0 ng/mL
What causes an increase of prolactin?
- Pituitary adenoma
- Chronic renal failure
- Side effect of certain drugs
Hyperprolactinemia results in __________
What causes a decrease in prolactin?
Tumor that compresses or replaces normal pituitary tissue
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