Exam #4: Anterior & Posterior Pituitary Flashcards
(41 cards)
What are polypeptide hormones? List examples of polypeptide hormones.
Polypeptide hormones are hormones that have LESS THAN 100 amino acids & are often just called “peptide hormones”
- Oxytocin is an example
What are protein hormones? List examples of protein hormones.
Polypeptide hormones with MORE THAN 100 amino acids
- Growth hormone is an example
What are steroid hormones? List examples of steroid hormones.
Hormones that are derived from cholesterol
1) Adrenal steroid hormones including:
- Aldosterone
- Cortisol
- Adrenal androgens
2) Gonadal steroid hormones
- Testosterone from the testis
- Progesterone from the ovaries
3) Placental steroid hormones
- Estrogen & progesterone from the placenta
4) Vitamin D
What are amine hormones? List examples of amine hormones.
Amino-acid derived hormones such as the tyrosine derivatives
- Tyrosine–>DA, NE, & Epi
- Thyroid hormone: tyrosine derivative + iodine
Which types of hormone are water soluble? Describe the synthesis and release of these hormones.
Polypeptide and protein hormones are are water soluble
1) Synthesized as a large preprohormone (inactive)
2) Cleaved into prohormone in the ER & sent to golgi
3) Golgi packages into vesicles and cleaves to active hormone
4) Activate hormones are released via exocytosis
Which types of hormone are lipid soluble? Describe the synthesis and release of these hormones.
Steroid hormones are lipid soluble
1) Synthesized from cells that store cholesterol esters
2) Lipid soluble; thus, CANNOT be STORED in vesicles
3) Diffuse through the membrane and are directly released into the ISF after synthesis
*However, note that steroid hormones do bind to plasma proteins; this prevents clearance through the kidney and INCREASES the half-life of the hormone
Which hormones bind to surface receptors?
Peptide or protein hormones bind to surface receptors
*Note that this includes catecholamines (derived from the amino acid, tyrosine)
Which hormones bind to receptors in the cytosol or the nucleus? What happens after binding to the intracellular receptors? Outline the action of Leptin in terms of intracellular binding.
Steroid (i.e. lipophilic) hormones are intracellular hormones that bind with receptors in the cytosol or nucleus
- “Cytoplasmic receptors”
- “Nuclear receptors”
- ->These receptor complexes the bind to hormone response elements that alter DNA expression
Describe response driven negative feedback.
Response-driven negative feedback
1) Endocrine gland releases hormone
2) Hormone acts on target organ
3) Target organ exerts a physiologic effect
4) Negative feedback is exerted on the endocrine organ
Describe the endocrine-axis negative feedback system.
Endocrine-axis negative feedback
1) Hypothalamic neuroendocrine neurons
2) Releasing hormone
3) Pituitary gland
4) Tropic hormone
5) Peripheral endocrine gland
6) Hormone–>negative feedback onto the pituitary and hypothalamus
- Hormone has a effect on a target organ, which exerts physiological effects
- *Also, note that problems can arise at the three different levels of this pathway
Describe the anatomical relationship between the hypothalamus and the pituitary gland.
- The “hypo-thalamus” is located below the thalamus in the medial and lateral walls of the 3rd ventricle;
- Hypothalamus contains”primary plexus” or vessels that form a direct link between the anterior pituitary and they hypothalamus;
- “primary plexus” arises from the “median eminence” of the hypothalamus
- The anterior pituitary is inferior to the hypothalamus & contains the “secondary plexus”
These two anatomical locations are connected via portal hypophysial vessels or hypophysial stalk
Describe the physiological relationship between the hypothalamus and the pituitary gland. What is the difference between ultrashort, short, and long loop negative feedback?
- Hypothalamus releases substances that affect the anterior pituitary gland
- Ultra-short= hypothalamus effect on hypothalamus
- Short= ant. pit. on hypothalamus
- Long= end organ–>hypothalamus
What hormones are made and released by the hypothalamus?
Generally, remember that the hypothalamus makes “hypophysiotrophic hormones” or releasing/ inhibiting factors that act on the anterior pituitary
1) CRH= corticotropin-releasing hormone
2) TRH= thyrotropin releasing hormone
3) Gonadotropin-releasing hormone
4) GHRH= Growth hormone -releasing hormone
5) Somatostatin= growth hormone-inhibiting hormone
6) Dopamine= prolactin-inhibiting factor
What is the action of each hypothalamic hormone on the anterior pituitary?
1) CRH= corticotropin-releasing hormone= control of corticotropin or ACTH release
2) TRH= thyrotropin releasing hormone=
- Thyroid stimulating hormone
- Prolactin secretion
3) Gonadotropin-releasing hormone= FSH and LH
4) GHRH= Growth hormone -releasing hormone
5) Somatostatin= growth hormone-inhibiting hormone
6) Dopamine= prolactin-inhibiting factor
Which hormones are made by hypothalamic cells and released by the posterior pituitary?
ADH (vasopressin)= anti-diuretic hormone
Oxytocin= milk letdown & uterine contraction
Where are posterior pituitary hormones made? (Know names of the two hypothalamic nuclei)
Supraoptic
Paraventricular nuclei
Be able to list the anterior and posterior pituitary hormones and give their functions.
- ACTH= acts on the adrenal cortex to stimulate the release of cortisol
- TSH= Thyroid-Stimulating Hormone= control of the release of T3 & T4 from the thyroid gland (T3 is the active form) & stimulates the release of prolactin
- FSH= growth of follicles and sperm
- LH= ovulation of eggs
- Growth Hormone= goes to the liver, which makes insulin-like growth factors (IGF/somatomedin)
- Prolactin= make the milk, NOT MILK LETDOWN!!!!!!
Explain how hormones can be cleared form the blood.
1) Metabolic destruction by tissue or blood enzymes
2) Binding to tissue
3) Excretion by liver in the form of bile
4) Excretion from kidney in urine
- Liver is the most important side for degradation
- Kidney is also important
How does whether of not the hormone is free or bound to a protein carrier affect its half-life in the blood?
Binding to a protein carrier increases the half-life of a protein; prevents renal clearance b/c plasma proteins cannot be filtered
Describe the different types of diabetes insipidus.
1) Central= issue with the hypothalamus
- Tumor
- Trauma
- Surgery
2) Nephrogenic= problem in the kidney; this is an ADH unresponsive kidney
- Renal disease
- ADH-unresponsive kidney
- Drugs
*****Loss of water due to polyuria
Describe the actions of oxytocin and the stimulus for the milk let down reflex
Prolactin= make milk Oxytocin= milk letdown (connection from the nipple/breast to hypothalamus-->posterior pituitary)
Describe the physiological functions of growth hormone in the adipose tissue, muscle, and liver.
-Growth hormone goes to the liver, which releases insulin-like growth factors (IGF-I) OR growth hormone from the liver goes directly to the tissues and has an effect:
Adipose:
1) Increases breakdown of fat
2) Decreases glucose uptake
Muscle:
1) Increase protein synthesis
2) Decrease glucose uptake
Liver:
1) Increase gluconeogenic enzymes
2) Production of IGF
Remember, GH has three main functions:
- Diabetogenic effect
- Increased protein synthesis & organ growth
- Increased linear bone growth
What is the effect of growth hormone on bone growth?
Growth hormone causes an increase in linear bone growth
Describe the relationship between growth hormone and the insulin like growth factors.
- Growth hormone increases the release of IGF
- IGF exerts negative feedback on growth hormone
