What is the function of calcitonin in the intestine?
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Calcitonin inhibits calcium absorption in the intestine.
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What is the function of calcitonin in the intestine?
Calcitonin inhibits calcium absorption in the intestine.
What is the drug form of PTH and its characteristics?
The drug form of PTH is Teriparatide, which is a protein hormone consisting of 84 amino acids and is secreted from the chief cells of the parathyroid gland.
What are the types of Tyrosine Kinase Receptors and their associated growth factors?
Receptor | Associated Growth Factor |
---|---|
TRK A | Nerve Growth Factor |
TRK B | Brain Derived Growth Factor |
TRK C | Neurotrophin |
What are the main types of cell membrane receptors?
The main types of cell membrane receptors include:
What is the inactive state of cytoplasmic steroid hormone receptors?
In the inactive state, steroid hormone receptors are located in the cytoplasm and are bound to heat shock proteins. When a hormone binds to the receptor, it activates the complex, allowing it to enter the nucleus.
What are some examples of nuclear receptors?
Examples of nuclear receptors include:
What is the mechanism of action of G-Protein Coupled Receptors (GPCRs)?
The mechanism of action of GPCRs involves the following steps:
What are some functions of second messengers in hormonal action?
Functions of second messengers include:
Second Messenger | Hormone | Function |
---|---|---|
cAMP | Vasopressin (va) | Water reabsorption |
Glucagon | Metabolism | |
Secretin | Electrolyte (HCO3-) secretion | |
Calcium (IP3 - DAG) | Vasopressin (vi), Endothelin | Vasoconstriction |
Oxytocin | Uterine contraction | |
- | Exocytosis | |
cAMP | Nitric Oxide | Vasodilatation |
Natriuretic Peptides | Relaxation |
What is the role of leptin as a permissive hormone in early puberty?
Leptin plays a crucial role in signaling energy status to the hypothalamus, which is essential for the onset of puberty. It influences the secretion of gonadotropin-releasing hormone (GnRH), thereby affecting the development of secondary sexual characteristics.
What are the main functions of prolactin in lactation?
Prolactin is responsible for the initiation of milk secretion (lactogenesis) and the maintenance of lactation (galactopoiesis). It stimulates mammary gland development and milk production in response to suckling.
What hormones are released by the anterior pituitary and their corresponding cell types?
Cell Type | Hormone(s) |
---|---|
Somatotrope | Growth Hormone |
Lactotrope | Prolactin |
Gonadotrope | FSH, LH |
Thyrotrope | TSH |
Corticotrope | ACTH |
What is the significance of negative feedback in endocrine hormone release?
Negative feedback is a regulatory mechanism that helps maintain homeostasis in the endocrine system. It involves the inhibition of hormone release by the effects of the hormone itself or by the hormones produced by target glands, ensuring that hormone levels remain within a normal range.
What are the effects of ACTH on the body, particularly in relation to Addison's disease?
ACTH stimulates the adrenal cortex to produce cortisol. In Addison's disease, there is an underproduction of cortisol, leading to increased levels of ACTH. This can result in symptoms such as hyperpigmentation due to the excess ACTH mimicking the action of melanocyte-stimulating hormone (MSH).
What are the hypothalamic releasing hormones and their corresponding hormones released from the anterior pituitary?
Hypothalamic Hormone | Anterior Pituitary Hormone(s) |
---|---|
Thyrotropin-releasing hormone (TRH) | TSH, Prolactin |
Corticotropin-releasing hormone (CRH) | ACTH |
Gonadotropin-releasing hormone (GnRH) | LH, FSH |
Growth hormone-releasing hormone (GHRH) | GH |
What are the roles of hypothalamic inhibiting hormones in the anterior pituitary?
Hypothalamic Inhibiting Hormone | Role in Anterior Pituitary |
---|---|
Prolactin release-inhibiting hormone (PIH)/dopamine | Inhibits prolactin release |
Growth hormone release-inhibiting hormone/somatostatin | Inhibits GH release |
What factors increase and inhibit growth hormone secretion?
Factors Increasing GH Secretion | Factors Inhibiting GH Secretion |
---|---|
Hypoglycemia | Somatostatin |
Exercise | Increased blood glucose (e.g., infusion) |
Fasting | REM sleep |
Stress | |
Starvation | |
Deep sleep (NREM stage 3 & 4) |
What are the direct actions of growth hormone?
What are the direct actions of Growth Hormone (GH) mediated by the JAK-STAT pathway?
The direct actions of GH mediated by the JAK-STAT pathway include:
What are the indirect actions of Growth Hormone (GH) mediated by IGF-1?
The indirect actions of GH mediated by IGF-1 primarily involve:
What disorders are associated with abnormal levels of Growth Hormone (GH) in children?
In children, disorders associated with abnormal levels of GH include:
What are the features of Acromegaly in adults?
Features of Acromegaly include:
What are the treatment options for Acromegaly?
Treatment options for Acromegaly include:
Surgical Treatment:
Pharmacological Treatment:
What is Laron dwarfism and its etiology?
Laron dwarfism, also known as GH insensitivity syndrome, is characterized by:
What are the uses of Recombinant Human Growth Hormone?
Recombinant Human Growth Hormone is used in:
What are the primary effects of prolactin on the body?
What factors increase prolactin secretion?
Factors increasing prolactin secretion include:
What factors inhibit prolactin secretion?
Factors inhibiting prolactin secretion include:
How does the hypothalamus regulate prolactin secretion?
The hypothalamus regulates prolactin secretion by releasing Thyrotrophin releasing hormone (TRH) which stimulates lactotrophs in the anterior pituitary to produce prolactin. Additionally, glucocorticoids and thyroid hormones inhibit prolactin secretion, as does the prolactin inhibiting factor (Dopamine).
What are the raw materials required for thyroid hormone synthesis?
The raw materials required for thyroid hormone synthesis are:
What is the function of the Sodium Iodide Symporter (NIS) in thyroid hormone synthesis?
The Sodium Iodide Symporter (NIS) is located at the basolateral end of follicular cells and functions in iodide trapping through 2º active transport. It is also found in other locations such as the salivary gland, mammary gland, and placenta.
What is the wolf-Chaikoff effect and its clinical use?
The wolf-Chaikoff effect is the phenomenon where excess iodide, through the sodium-iodide symporter (NIS), inhibits the organification of iodide, leading to decreased synthesis of thyroid hormones T3 and T4. Clinically, it is used in the treatment of patients with hyperthyroidism by administering Lugol's iodine prior to thyroid surgery.
What are the consequences of mutations in the iodide-chloride antiporter/pendrin?
Mutations in the iodide-chloride antiporter/pendrin can lead to:
What is the function of Thyroid Peroxidase (TPO) in thyroid hormone synthesis?
Thyroid Peroxidase (TPO) is an enzyme that catalyzes the oxidation of iodide to iodine, which is essential for the synthesis of thyroid hormones T3 and T4. It plays a crucial role in the organification of iodide, which is necessary for the production of these hormones.
What is the role of binding proteins in the transport of thyroid hormones?
Thyroid hormones T3 and T4 are predominantly bound to binding proteins in the blood, with 99% of them being bound and only 1% free, which is responsible for their biological actions. The main binding proteins include:
How do T3 and T4 enter target cells and what is their mechanism of action?
T3 and T4 enter target cells through transporters such as monocarboxylate transporter (MCT) and organic anion transporting polypeptide (OATP). Once inside the cell, they bind to nuclear receptors in the nucleus, where they regulate gene expression and influence metabolic processes.
What are the differences in potency and half-life between Triiodothyronine (T₃) and Thyroxine (T₄)?
Hormone | Potency | Half-life |
---|---|---|
T₃ | Most potent | 1 day |
T₄ | Least potent | 7 days |
How do T₃ and T₄ differ in their plasma protein binding and action duration?
Hormone | Plasma Protein Binding | Action Duration |
---|---|---|
T₃ | Less | Acts rapidly |
T₄ | More | Long-lasting |
What are the physiological effects of thyroid hormones on the heart?
Thyroid hormones have a chronotropic and inotropic effect on the heart by increasing the number of β-adrenergic receptors, mediated by norepinephrine.
How do thyroid hormones affect adipose tissue and muscle?
Thyroid hormones stimulate lipolysis in adipose tissue (catabolic effect) and increase proteolysis in muscle (catabolic effect).
What developmental effects do thyroid hormones have on the CNS and bone?
Thyroid hormones promote brain growth through increased myelination in the CNS and support normal growth and skeletal development in bones.
What is the impact of T₃ on glycosaminoglycans (GAGS) and what condition can result from hypothyroidism?
T₃ prevents the accumulation of GAGS, while hypothyroidism leads to their accumulation, resulting in myxedema and puffiness of the face.
What are the consequences of congenital hypothyroidism on mental and physical development?
Congenital hypothyroidism can lead to mental retardation (most common reversible cause) and stunted growth.
How does T₃ affect respiration and oxygen consumption in the lungs?
T₃ increases metabolism and oxygen consumption, leading to hypoxia and a right shift of the oxygen dissociation curve, which stimulates respiration and increases respiratory rate.
What is the role of T4 deiodinase in the conversion of T4 to T3?
T4 deiodinase catalyzes the conversion of T4 (thyroxine) to T3 (triiodothyronine) and contains the amino acid selenocystine.
How does T3 influence thermogenesis in the body?
T3 stimulates uncoupling protein I (UCPI), leading to heat dissipation and thermogenic action, which increases heat production in the body.
What are the effects of hyperthyroidism and hypothyroidism on heat generation?
Hyperthyroidism results in increased heat generation and heat intolerance, while hypothyroidism leads to no heat generation and cold intolerance.
What are the secretions of the different cell types in the endocrine pancreas?
Cell type | Secretion |
---|---|
A cells (Alpha) | Glucagon |
B cells (Beta) | Insulin, Amylin, C peptide |
D cells (Delta) | Somatostatin |
F cells | Pancreatic polypeptide |
What are some properties of insulin?
What are the steps involved in the release of insulin from beta cells of the pancreas?
What are the sites of insulin-dependent glucose uptake?
Note: Exercise activates the AMP-activated kinase pathway, which also increases GLUT-4 independently of insulin, benefiting diabetics.
What are the rapid and long-term actions of insulin?
Rapid actions (within seconds):
Long-term actions (in days):
What are the two main signaling pathways activated by insulin and their functions?
PI3 Kinase pathway (PI3K):
MAP Kinase pathway (MAPK):
What is the clinical significance of insulin in relation to blood glucose levels?
Insulin is a hypoglycemic hormone; a decrease in blood glucose levels can lead to coma if levels drop below 30 mg/dl. It plays a crucial role in maintaining glucose homeostasis, especially after protein meals where insulin and glucagon levels increase.
What factors increase insulin secretion?
Factors that increase insulin secretion include:
What factors decrease insulin secretion?
Factors that decrease insulin secretion include:
What are the metabolic pathways stimulated and inhibited by insulin?
Pathways Stimulated by Insulin | Pathways Inhibited by Insulin |
---|---|
↑ Glycolysis | ↓ Glycogenolysis |
↑ Glycogenesis | ↓ Gluconeogenesis |
↑ Lipogenesis | ↓ Lipolysis |
What hormones mediate ketogenesis in response to hyperglycemia?
Ketogenesis is mediated by hyperglycemic/counter-regulatory hormones, which include:
What are the main secretions of the adrenal gland?
The adrenal gland has different zones that secrete various hormones:
What is the major source of testosterone in the body?
The major source of testosterone is the testis.
What is the role of the hypothalamic-pituitary-adrenal (HPA) axis in hormone synthesis?
The HPA axis regulates hormone synthesis through a feedback loop where the hypothalamus releases corticotropin-releasing hormone, stimulating the anterior pituitary to release adrenocorticotropic hormone, which in turn stimulates the adrenal cortex to produce cortisol, aldosterone, and adrenal sex steroids.
What is the half-life of aldosterone and its significance?
Aldosterone has a half-life of 20 minutes and is considered a life-saving steroid hormone due to its critical role in regulating sodium and potassium levels in the body.
What are the sites of mineralocorticoid receptor (MR) action in the body?
The mineralocorticoid receptor (MR) is found in the kidneys, colon, hippocampus, salivary glands, and sweat glands.
What is the significance of enzyme deficiencies in adrenal hormone synthesis?
Deficiencies of enzymes involved in adrenal hormone synthesis can lead to Congenital adrenal hyperplasia, a condition that affects hormone production and can have significant clinical implications.
What is the primary action of aldosterone in the kidneys?
Aldosterone primarily promotes the reabsorption of sodium (Na⁺) through epithelial sodium channels (ENaC) and facilitates the excretion of potassium (K⁺) via renal outer medullary potassium channels (ROMK).
What is Liddle's syndrome and how is it related to aldosterone?
Liddle's syndrome is characterized by a gain of function mutation of ENaC, leading to increased sodium reabsorption, which results in hypertension as a key manifestation.
What is the significance of aldosterone escape in hyperaldosteronism?
Aldosterone escape refers to the phenomenon where an increase in extracellular fluid (ECF) does not lead to edema despite hyperaldosteronism, which results in increased sodium (Na⁺) levels.
How does aldosterone affect potassium levels in the body?
Aldosterone facilitates the excretion of potassium (K⁺) through renal outer medullary potassium channels (ROMK), which helps regulate potassium levels in the body.
What role does atrial natriuretic peptide play in relation to aldosterone?
Atrial natriuretic peptide promotes natriuresis, which is the excretion of sodium in urine, counteracting the effects of aldosterone and preventing edema.
What stimulates aldosterone release in the body?
Hyperkalemia stimulates aldosterone release, while ACTH increases aldosterone levels transiently.
What are the clinical features of Conn's syndrome associated with hyperaldosteronism?
The clinical features of Conn's syndrome include:
What is aldosterone escape and how does it occur?
Aldosterone escape refers to the phenomenon where there is Na+ and H₂O excretion despite increased aldosterone levels, due to:
What are the features of Addison's disease related to hypoaldosteronism?
Feature | Description |
---|---|
Hyponatremia | Low sodium levels |
Postural hypotension | Drop in blood pressure on standing |
Hyperkalemia | High potassium levels |
Microcardia | Small heart size |
What are the main functions of sex steroids?
The main functions of sex steroids include:
What are the causes of increased adrenal androgens in disorders?
Cause | Description |
---|---|
Adrenocortical tumors | Tumors of the adrenal cortex |
Congenital adrenal hyperplasia | Enzyme deficiency in adrenal hormone synthesis |
Adrenogenital syndrome | Excess androgen production |
What are the pathological effects of Cushing's syndrome due to cortisol excess?
Pathological Effect | Description/Manifestation |
---|---|
Muscle weakness & proximal myopathy | Steroid myopathy |
Glucose intolerance & diabetes mellitus | Adrenal diabetes |
Dyslipidemia | Abnormal lipid levels |
Buffalo hump & moon face | Fat redistribution |
Increased susceptibility to infections | Immunosuppression |
Eosinopenia | Low eosinophil count |
Hypercoagulable state | Increased risk of thrombosis |
Irritability & psychosis | Neuropsychiatric symptoms |
Hypertension & atherosclerosis | High blood pressure & arterial disease |
Hypercalciuria & renal stones | Increased calcium in urine, kidney stones |
Peptic ulcer | Increased gastric acid |
Amenorrhea, loss of libido, infertility | Reproductive dysfunction |
How does cortisol affect carbohydrate metabolism?
Cortisol acts as a 'hyperglycemic hormone' by increasing gluconeogenesis, which raises blood glucose levels.
What is the effect of cortisol on protein metabolism?
Cortisol has a catabolic effect in muscle, leading to proteolysis, while it has an anabolic effect in the liver, increasing the synthesis of plasma proteins.
What is the role of cortisol in fat metabolism?
Cortisol is lipolytic, meaning it promotes the breakdown of fats.
How does cortisol influence the immune system?
Cortisol acts as an anti-inflammatory agent, reducing inflammation and immune responses.
What changes in blood cell levels are caused by cortisol?
Cortisol decreases the blood levels of eosinophils and lymphocytes while increasing the levels of neutrophils, platelets, and red blood cells (RBCs).
What effects does cortisol have on the nervous system?
Cortisol alters mood and behavior and increases appetite.
How does cortisol affect kidney function?
Cortisol increases the glomerular filtration rate and calcium excretion in the kidneys.
What impact does cortisol have on bone health?
Cortisol increases bone resorption by enhancing the activity of osteoclasts, which can lead to bone loss.
What is the effect of cortisol on connective tissues?
Cortisol inhibits fibroblast proliferation and collagen formation, which can delay wound healing and cause purple striae on the skin.
How does cortisol influence the gastrointestinal tract?
Cortisol increases gastric acid secretion, which can lead to peptic ulcers.
What reproductive effects does cortisol have?
Cortisol inhibits GnRH, leading to amenorrhea, loss of libido, and infertility.
What are the main adrenal sex steroids found in both males and females?
Steroid | Description |
---|---|
Dehydroepiandrosterone (DHEA) | Precursor to androgens/estrogens |
Dehydroepiandrosterone sulfate (DHEAS) | Sulfated form of DHEA |
Androstenedione | Precursor to testosterone/estrogens |
Testosterone (small amounts) | Main male sex hormone (minor from adrenals) |
What are the normal serum calcium levels?
Normal serum calcium levels range from 9 to 11 mg/dL.
What is the relationship between ionized calcium and protein-bound calcium?
Ionized calcium and protein-bound calcium each make up 50% of total calcium in the serum, with ionized calcium being the physiologically active form and protein-bound calcium being the inactive form.
How does respiratory alkalosis affect calcium levels?
In respiratory alkalosis, the decrease in H⁺ ions causes calcium to bind to albumin, increasing the bound form of calcium and decreasing the free form, which can lead to hypocalcemic tetany.
What are the three forms of calcium distribution in the body and their respective percentages?
Form | Percentage |
---|---|
Free form | 50% |
Bound form | 41% |
Complex form | 9% |
What is the mechanism behind hypocalcemic tetany?
What are the signs of hypocalcemic tetany?
Trousseau's sign: Eliciting carpopedal spasm by inflating a sphygmomanometer 20 mm Hg above SBP for 3 minutes.
Chvostek's sign: Facial muscle twitching upon tapping the facial nerve at the angle of the jaw.
What is the role of parathyroid hormone (PTH) in calcium absorption?
How does teriparatide affect bone metabolism?
What is the overall action of PTH on the kidneys regarding calcium reabsorption?
PTH increases calcium reabsorption in the kidneys, specifically in the distal convoluted tubule (DCT) and proximal convoluted tubule (PCT). It also promotes phosphaturia through the Na+ PO4- cotransporter, leading to increased excretion of phosphate in urine.
How does PTH affect calcium absorption in the gastrointestinal tract?
PTH indirectly increases calcium absorption from the gastrointestinal tract by enhancing the synthesis of Vitamin D, which in turn promotes calcium absorption from the diet.
What is the role of calcium sensing receptors (CaSR) in relation to PTH?
Calcium sensing receptors (CaSR) help regulate PTH secretion. A mutation in CaSR can lead to a condition where PTH is not suppressed, resulting in elevated levels of PTH and causing familial hypocalciuric hypercalcemia.
What is the source of calcitonin and its primary action?
Calcitonin is produced by the parafollicular C cells of the thyroid gland. Its primary action is to lower blood calcium levels by inhibiting osteoclast activity, thus reducing bone resorption.
What are the two types of bone markers and examples of each?
Bone markers are classified into two types:
Bone formation markers:
Bone resorption markers:
What are the facilitating and inhibiting factors for calcium absorption in the duodenum?
Facilitating factors for calcium absorption include gastric acid and a protein-rich diet. Inhibiting factors include phytates and oxalates, which form insoluble complexes that hinder absorption.
What is the overall effect of PTH, Vitamin D, and Calcitonin on serum calcium and phosphate levels?
Hormone | Serum Calcium | Serum Phosphate |
---|---|---|
PTH | ↑s. Ca²⁺ | ↓s. phosphate |
Vitamin D | ↑s. Ca²⁺ | ↑s. phosphate |
Calcitonin | ↓s. Ca²⁺ | - |
What is the role of PTH in the kidney?
PTH increases phosphate excretion by inhibiting the Sodium Phosphate cotransporter in the proximal convoluted tubule (PCT).