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 Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle

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مُساهمةموضوع: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الإثنين أكتوبر 18, 2010 8:14 pm

why hypocalcemia increases CNS  excitability

When extracellular calcium falls below normal, the nervous system becomes progressively more excitable because of increase permeability of neuronal membranes to sodium


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how vitamin D affects osteoclasts


Osteoblasts, but not osteoclasts have vitamin D receptors.  
1,25-(OH)2-D acts on osteoblasts which produce a paracrine signal that activates osteoclasts to resorb Ca++ from the bone matrix.  



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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الإثنين أكتوبر 18, 2010 8:25 pm

how parathyroid hormone is regulated

The dominant regulator of PTH is plasma Ca2+.
Secretion of PTH is inversely related to [Ca2+].  
Maximum secretion of PTH occurs at plasma Ca2+ below 3.5  mg/dL.
At Ca2+ above 5.5 mg/dL, PTH secretion is maximally inhibited.  

PTH secretion responds to small alterations in plasma Ca2+ within seconds.  
A unique calcium receptor within the parathyroid cell plasma membrane senses changes in the extracellular fluid concentration of Ca2+.  
This is a typical G-protein coupled receptor that activates phospholipase C and inhibits adenylate cyclase—result is increase in intracellular Ca2+ via generation of inositol phosphates and decrease in cAMP which prevents exocytosis of PTH from secretory granules.


When Ca2+ falls, cAMP rises and PTH is secreted.  
1,25-(OH)2-D inhibits PTH gene expression, providing another level of feedback control of PTH.  
Despite close connection between Ca2+ and PO4, no direct control of PTH is exerted by phosphate levels.




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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   السبت يونيو 02, 2012 4:55 am

What is the effect of PTH on blood calcium level?







PTH is a calcium raising hormone through: (refer to lecture)

1-increasing calcium reabsorption from kidney tubules.
2-increasing calcium absorption from intestine (by the help of 1,25 DHCC).
3-increasing bone resorption (via stimulation of osteoclasts).






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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الأربعاء أكتوبر 14, 2015 6:32 am

WHY DOES POLYPHAGIA OCCUR WITH DIABETES MLLITUS?
===========
ANSWER:
=======
First reason for polyphagia: is the intracellular starvation. As in diabetes either there is absence or the resistance to insulin action so glucose cannot move into the cells and thus cells are starved of glucose.The cellular response to glucose starvation manifests in the form of frequent hunger pangs. Body cells use hormones like leptin and orexin to stimulate the hypothalamus of the brain, which eventually causes the desire to eat food. Thus, hunger signals sent out by the body cells and then received by the brain, is what causes excessive eating in diabetic patients.

Second reason can be: the "Glucostat theory of feeding regulation". According to this theory arteriovenous difference of glucose in the hypothalamic satiety and feeding centers regulate the feeding response. If the difference is high due to the reason that glucose is more utilized by satiety center, the satiety center is activated. And if the difference is low then feeding center is activated. In diabetes due to insulin resistance or absence of insulin, glucose cannot move into the satiety center thus the arteriovenous difference remains low and the feeding center is chronically active.

Thus polyphagia occurs.
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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الثلاثاء ديسمبر 08, 2015 6:36 am


What is effect of estrogen and progesterone on body water content during pregnancy?


================

Answer

Estrogen and progesterone are increased during pregnancy increasing total body water through acting on renal tubules. In high levels during pregnancy, they cause salt & water retention. Progesterone acts mainly on distal tubules of the kidney and to be noted at its normal level, it causes natriuresis (sodium loss in urine).





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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الثلاثاء ديسمبر 29, 2015 5:42 pm

Question


A 6-year-old boy showed appearance of hair in his face, axillary and pubic area and deepening in his voice. After investigation, he was diagnosed as a precocious puberty due to a pituitary tumor.
The hormone profile shows
Low levels of GnRH, high levels of FSH, LH and testosterone. Explain this hormone profile
============
Answer

The tumor in pituitary causes increased secretion of FSH & LH which in turn increases testosterone secretion. so, there will be increased FSH, LH & Testosterone which all of these cause negative feedback with hypothalamus resulting in decrease in GnRH.

==========



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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الثلاثاء يناير 26, 2016 9:30 pm

Question

How excess ADH secretion causes hyponatremia?

==========
Answer

ADH is a hormone secreted by posterior pituitary normally and it causes water retention through increasing water reabsorption from the distal renal tubules. in certain conditions, some tumors are secretory like that secrete ADH causing SIADH syndrome resulting in excessive water reabsorption and increasing blood volume leading to hyponatremia (decreased sodium level) which results from an excess of water rather than a deficiency of sodium

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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الإثنين مارس 07, 2016 10:40 am

Q: Outline the physiological basis of Pathological outcomes of chronic stress
============

A: The physiological basis of Pathological outcomes of chronic stress


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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الإثنين مارس 21, 2016 10:26 pm

Q: Why there is amenorrhea in females performing severe exercises?
=================
A: In females who performed strenous (severe) exercise develop a condition termed exercise amenorrhea which is due to hyperprolactinemia in this case which causes the following:
1-Decrease in GnRh.
2-Decrease in GnH.
3-Decrease in sensitivity of ovaries to GnH.
So, the net result is inhibition of hypothalamo-hypophyseal-gonadal axis resulting in amenorrhea.


NB: Stress that occurs with severe exercise also increases prolactin secretion

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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الأحد مارس 27, 2016 4:04 pm

Q: Mention the function of Cowper's glands in the male reproduction
====================
A: The semen is formed of sperms and seminal fluids which arise from seminal vesicles, prostate and Cowper's glands. The the Cowper’s glands begin producing an alkaline mucous secretion known as pre-ejaculate. Pre-ejaculate neutralizes acidic urine that may still be present in the urethra while also lubricating the urethra and external urethral orifice to
protect sperm from mechanical damage during ejaculation.



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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الإثنين مايو 02, 2016 5:56 am

Question

What is priapism?
================
Answer

Priapism is a potentially painful medical condition in which the erect penis does not return to its flaccid state, despite the absence of both physical and psychological stimulation, within four hours. It may be associated with haematological disorders, especially sickle-cell disease, sickle-cell trait, and other conditions such as leukemia, thalassemia, and neurologic disorders such as spinal cord lesions and spinal cord trauma. It may also be associated with glucose-6-phosphate dehydrogenase deficiency, which leads to decreased NADPH levels. NADPH is a co-factor involved in the formation of nitric oxide, which may result in priapism. Raised levels of adenosine may also contribute to the condition
by causing blood vessels to dilate, thus influencing blood flow into the penis.




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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   السبت مايو 21, 2016 6:47 am

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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الخميس أكتوبر 06, 2016 9:34 am

Question
Mechanisms of Hypothyroidism-related Hypertension
Answer
====
1. It is associated with peripheral vasoconstriction
2. In the hypothyroid state, the density of α1-adrenoreceptors is increased while β-adrenoreceptors are reduced in vascular beds increasing VC.
3. It causes hypercholesterolemia, arteriosclerosis and changes in arterial wall elasticity
4. Deterioration of renal function: hyponatremia is the most common electrolyte derangement in hypothyroid patients and is associated with the inability of the hypothyroid kidney to excrete water overload
5. Water and sodium retention during severe hypothyroidism
6. Plasma vasopressin levels have been found to be increased in hypothyroidism, suggesting a possible role in total water retention.
7. Low body temperature is the common denominator between thyroid and fluid retention. Low thyroid function can lead to low temperatures and low temperatures can cause fluid retention or bloating, tight rings, swollen ankles, and puffy face and eyes.


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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الجمعة أكتوبر 07, 2016 8:56 am

Question
Mention the cause of menstrual disorders in thyroid dysfunction
===================
Answer

Thyroid dysfunction is associated with a range of menstrual abnormalities, including oligomenorrhea, amenorrhea, and menorrhagia. Women with hypothyroidism may also be at increased risk of pregnancy loss. The connection between thyroid hormone levels and the menstrual cycle is mainly mediated by thyrotropin-releasing hormone (TRH), which has a direct effect on the ovary. Additionally, abnormal thyroid function can alter levels of sex hormone-binding globulin, prolactin, and gonadotropin-releasing hormone, contributing to menstrual dysfunction. For example, increased levels of TRH may raise prolactin levels, contributing to the amenorrhea associated with hypothyroidism.




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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الإثنين نوفمبر 14, 2016 6:40 am

Question

What is pseudohypoparathyroidism?
=====
Answer

Pseudohypoparathyroidism is a condition associated primarily with resistance to the parathyroid hormone. Those with the condition have a low serum calcium and high phosphate, but the parathyroid hormone level (PTH) is actually appropriately high (due to the low level of calcium in the blood). Its pathogenesis has been linked to dysfunctional G Proteins (in particular, Gs alpha subunit)


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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الثلاثاء نوفمبر 22, 2016 5:28 pm

Questions
Why testosterone has higher plasma level than DHT
Why testosterone-receptor complexes are less stable in target cells
=======
Answer


The enzyme 5α-reductase catalyzes the formation of Dihydrotestosterone (DHT) from testosterone in certain tissues including the prostate gland, seminal vesicles, epididymides, skin, hair follicles, liver, and brain
Thus, logically the substrate (testosterone) is more than the product (DHT).

=====
DHT has an affinity to the human androgen receptor (AR) of about 2- to 3-fold higher than that of testosterone .The dissociation rate of DHT from the AR is 5-fold slower than that of testosterone. The half maximal effective concentration (EC50, the concentration of the hormone which induces a response halfway between the baseline and maximum after a specified exposure time) of DHT for activation of the AR is about 5-fold higher than that of testosterone.

The biological half-life (terminal half-life, the time taken by a substance to lose half of its physiologic, activity) of DHT in the body (53 minutes) is longer than that of testosterone (34 minutes), and this may account
for some of the difference in their potency


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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   السبت يناير 07, 2017 8:10 am

Question:
=======
WHICH HORMONE IS RESPONSIBLE FOR MALE SECONDARY SEX CHARACTERS, DHT OR TESTOSTERONE?
=======================================
Answer:
======
Testosterone and DHT are important for sexual development as well as secondary sexual characteristics such as thick skin and male-pattern hair growth
=========
For DHT:
-During male embryogenesis, DHT has an essential role in the formation of the male external genitalia.
-In the adult male, DHT acts as the primary androgen in the prostate gland, seminal vesicles, skin, and hair follicles.
-In congenital 5α-reductase deficiency, male pseudohermaphroditism results. It presents with underdeveloped male genitalia and prostate. Males with this condition are often raised as girls due to their lack of conspicuous male genitalia. At the onset of puberty, although their DHT levels remain very low, their testosterone levels elevate normally. Their musculature develops like that of other male adults. After puberty, men with this condition have a large deficiency of pubic and body hair and reportedly no incidence of androgenic alopecia (pattern hair loss).
=========
For Testosterone:
-It plays a key role in the development of male reproductive tissues such as the testis and prostate, as well as promoting secondary sexual characteristics such as increased muscle and bone mass, and the growth of body hair.
-In addition, it is essential for health and well-being, and for the prevention of osteoporosis.
-Insufficient levels of testosterone in men may lead to abnormalities including frailty and bone loss.




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مُساهمةموضوع: رد: Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle   الخميس فبراير 09, 2017 8:37 am

QUESTION
Mention how Gestational Diabetes affect fetus
=================================
ANSWER
Gestational diabetes means diabetes of pregnancy. it showed hyperinsulinemia and hyperglycemia. Insulin cannot cross the plancenta, but, glucose can do and causes fetal hyperglycemia which stimulates fetal pancreas increasing fetal insulin with its hazards including macrosomia i.e. newborn with an excessive birth weight


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Questions and answers on endocrine & Reproduction Physiology by dr khaled Abulfadle
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