Exam #4: Anterior & Posterior Pituitary Flashcards
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
List where the insulin-like growth factors and where they are produced.
Insulin-like growth factors (IGF) are produced in the liver
What is the other name for the insulin-like growth factors?
- IGF
- Somatomedin
Define term panhypopituitarism.
Panhypopituitarism is a condition of inadequate or absent production of the anterior pituitary hormones
What is the effect of panhypopituitarism?
No or lessened secretion of all the pituitary hormones
Describe the effect of too little growth hormone.
Dwarfism
Describe the effect of too much growth hormone.
- Overgrowth
- Insulin resistance
How do the effects of overabundance or too little growth hormone differ if present from birth or, of if it occurs during adulthood.
Dependent on the closure of the epiphyseal plates:
- Giantism prior to closure
- Acromegaly is after the closure of the epiphyseal plates
Describe the symptoms seen in patients with acromegaly.
Increased periosteal bone growth Increased organ size Increased hand and foot size Enlargement of the tongue Coarsening of the features Insulin resistance Glucose intolerance
What is the median eminence?
Part of the hypothalamus that contains the primary plexus
What are the of the portal circulation between the hypothalamus and anterior pituitary?
This is the network of blood vessels between the hypothalamus & the anterior pituitary
- Primary plexus (median eminance–>hypophysial vessels–>anterior pituitary
What is the hypothalamophypophysial tract?
This is the connection between the hypothalamus (supraoptic and paraventricular nuclei) and the posterior pituitary gland
What is a tropic hormone?
A tropic hormone is a hormone released from the hypothalamus that has an effect on group of cells in the anterior pituitary, causing growth of that region and secretion of its hormones
What are the three parts of a G-protein coupled receptor? Which parts can function independently?
Three parts: alpha, beta, and gamma
- Alpha
- Beta/gamma
What are the two different types of intracellular receptors?
1) Receptor is already attached to the DNA
2) Receptor is NOT attached to the DNA & must enter to nucleus to interact with its corresponding hormone response elements
What is the adenohypophysis? What is the neurohypophysis?
- Adeno= anterior pituitary
- Neuro= posterior pituitary
List the hormone secreting cells of the anterior pituitary.
Somatotrope Lactotrope Corticotrope Thyrotrope Gonadotrope
What is the function of Gherlin?
Acts on the Anterior Pituitary to increase the release of IGF-I from the liver
