Clinical Chemistry Blog Notes 07

Drug Testing

2009-09-09T21:44:00.000-07:00

Do You Think That Drug Testing Should be Done as a Requirement for Admission to Schools? Why or Why Not?

I can say that I strongly agree with this statement that drug testing should be done as a requirement for admission to schools. Nowadays I recognize that drug and alcohol abuse represents an emerging problem in society. Most of the population involved in this kind of problems are students in our society, thats why the schools has to be aware of this kind of problem and must perform a fundamental role to control and manage this problem. Having this kind of screening to the students may somehow help to reduce and control the abuse of drugs. But the major disadvantage is that enrolees will subsequently decrease in number which the school obviously does not want to happen. One major problem that this task may encounter is the confidentiality of the results must be strictly keep in privacy. But despite this disadvantages I think it will be helpful for all of us if drug testing will be implemented in every school in our society and bring awareness to each and every people.

Quiz on Negative Feedback Mechanism

2009-08-25T19:52:00.001-07:00

Questions

1. What is the physiological inhibition loop that controls the suppression and regulation of most endocrine hormones?

2. When TRH is released into the portal system it directs the thyrotrophs in the anterior pituitary to secrete ______________.

3. After negative feedback mechanism has occurred the hormone levels will tend to be _________.

4. When thyroxine is released in the blood and circulates to the hypothalamus and pituitary to suppress further ______ and ______ production.

5. The mechanism mainly depends on factors which maneuver the ________ and ______ of the hormones.

True or False

6. The high concentration of the hormone alone will trigger the negative feedback mechanism.

7. Negative feedback is generally termed as the response of the system in the same direction.

8. Negative feedback must be triggered by the effect and result of overproduction of the hormone.

9. Its major function is to bring the hormone levels back within the normal range.

10. Hypothalamic-pituitary-thyroidal axis is an example of an endocrine negative feedback loop.

Case Analysis

Discuss briefly what happens in the homeostatic negative feedback loop when a person’s thyroid hormone levels increases in the blood’s circulation.

Original Photo: by dube1111

Homeostatic Negative Feedback Control Mechanism

2009-08-13T07:03:00.000-07:00

Negative Feedback Mechanism

- It’s the physiological inhibition loop controlling most of the endocrine hormones. In negative feedback, any change or variation from the normal range of function is divergent, or resisted. The change or variation in the controlled value signals the response that brings the function of organ back within the normal range. The mechanism primarily depends on factors which manipulate the metabolism and flow of the hormones. Therefore, the high concentration of the hormone alone will not trigger the negative feedback mechanism because it must be triggered by the effect and result of overproduction on the hormone.

A simple example of an endocrine feedback loop is the hypothalamic-pituitary-thyroidal axis. The hypothalamus produces the hypophysiotropic hormone, thyrotropin-releasing hormone (TRH), and releases it into the portal system where it directs the thyrotrophs in the anterior pituitary to secrete thyroid-stimulating hormone (TSH). TSH circulates to the thyroid and stimulates several steps in the thyroid that are critical in the production and release of thyroid hormone. Thyroxine is released in the blood and circulates to the hypothalamus and pituitary to suppress further TRH and TSH production.

References: Fundamentals of Clinical Chemistry by Bishop et al

Clinical Laboratory Diagnosis by John Bernard Henry et al (19th Edition)

Images: original is File:ACTH Negative Feedback.jpg

My Top 10 List of Most Influential Bloggers

2009-07-28T23:14:00.000-07:00

Top 10 Emerging Influential Blogs of 2009:

1. Doctor Z of Zorlone- His blog is very inspiring and I would always love to read his poems which are simple yet they are able to make every reader enjoy reading his blog.

2. Roy The Struggling Blogger- I would say that this blog is a must see and read. One of my favorite blog because of the topics that are being posted are magnificently done.

3. Jan Geronimo of WritingToExhale- Reading this blog makes me think "how would a person be this very creative?". Very nice blog.

4. Angel Cuala of Father Blogger dot com-Family matters, is this blog all about. One of the blog that I always read and I also let my friends read his blog because it can help a lot especially to us teenagers.

5. Irene of LifeLots- I love the way she uses her everyday learning to inspire us and share life's ups and downs.

6. Luke of A Walk In The Dark- Very informative blog. I think this man is born to be a blogger. Two thumbs up for his works.

7. Holly Jahangiri of It’s all a matter of Perspective: Mine- Wide range of topics are being discussed. One of the must read.

8. Bingkee of I Love/Hate America- I have seen lots of blogs but I would tell that this is one of the best blog to read. Topics are very well discussed and very interesting to read.

9. Kelvin Servigon of Kelvinonian Ideas 2.0- Most of his blog are about updates on new gadgets and technology in our era. Which made me visit his blog more often. Very influential I suppose.

10. Dee of Tales From The Mom Side- Another nice piece of art. I am sure that the topics are being read by lots of moms.

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Pituitary Gigantism and Acromegaly

2009-07-14T05:10:00.001-07:00

Answers on the Growth Hormone Quiz

2009-06-30T05:08:00.000-07:00

1. Growth hormone releasing hormone
2. Sleeping
3-4. Pituitary dwarfism and Hypopituitarism
5. Skeletal muscles
6. Acromegaly
7. Laron's dwarfism
8. <5 ng/ml
9. 2-3 hours
10. Negative

Quiz on Growth Hormone

2009-06-16T07:55:00.000-07:00

1. What stimulate the release of the somatotropin from the pituitary gland?

2. The secretion of growth hormone is at its peak during ________.

3-4. Give two conditions which are caused by decreased levels of growth hormone.

5. Enhanced protein synthesis in this site is caused by the anabolic effects of growth hormone.

6. A coarse thickening of the bones of the skull, hands and feet over the course of years to decades.

7. An autosomal recessive disorder characterize by insensitivity to growth hormone, caused by a deviation of the growth hormone receptor. This disorder is associated with increased levels of GH.

8. Normal values of growth hormone in adult males?

9. Growth hormone is secreted in pulses, with an average interpulse interval of____ hours?

10. Obesity and the use of many drugs will cause false _______ result in the growth hormone suppression test.

Case Study

A 48-year-old man seeks care for evaluation of muscle weakness, headaches, and excessive sweating. He has poorly controlled hypertension and, on questioning, admits to noticing a gradual increase in both glove and shoe size, as well as a reduction in libido. A review of older photographs of the man documents coarsening of facial features, progressive prognathism and broadening of the nose. Acromegaly is suspected.

Questions:

1. What screening tests are available?

2. What is the definitive test for autonomous growth hormone production?

3. Because the patient complains of reduced libido, hypogonadism is suspected. What evaluation is appropriate?

Growth Hormone

2009-06-01T07:05:00.000-07:00

Growth Hormone

Growth hormone, also known as somatotropin for its growth-promoting effects on the body, also abundant hormone of the anterior pituitary. The major physiological effects of GH are anabolic: promoting protein synthesis, lipolytic, stimulating fat breakdown, lactogenic, diabetogenic by increasing resistance to insulin. Somehow, it also has intrinsic insulin-like hypoglycemic activity. Release of somatotropin from the pituitary is stimulated by the hypothalamic peptide growth hormone-releasing hormone (GHRH); somatotropin’s secretion is inhibited by somatostatin.

Growth hormone is secreted in pulses, with an average interpulse interval of 2-3 hours, with the most reproducible peak occurring at the onset of sleep. Complete absence of GH slows the rate of growth to only one third to one half of normal. Abnormally elevated levels lead to gigantism. In the adult patient with GH excess, no effects are seen in the long bones after the epiphyseal growth plates have fused. Instead, GH excess gradually produces acromegaly, a coarse thickening of the bones of the skull, hands and feet over the course of years to decades.

Functions of the Growth Hormone

Growth hormone has many diverse effects on metabolism; it is considered an amphibolic hormone because it directly influences both anabolic and catabolic processes. Increased height during childhood is the most widely known effect of GH.

Addition to increasing height in children and adolescents, growth hormone has many other effects on the body:

Increases calcium retention, and strengthens and increases the mineralization of bone
Increases muscle mass through sarcomere hyperplasia
Promotes lipolysis
Increases protein synthesis
Stimulates the growth of all internal organs excluding the brain
Plays a role in fuel homeostasis
Reduces liver uptake of glucose
Promotes gluconeogenesis in the liver
It contributes to the maintenance and function of pancreatic islets
It stimulates the immune system

Methods of Determination

Growth Hormone (hGH); Somatotropin

Human growth hormone (somatotropin, hGH) is essential to the growth process and has an important role in the metabolism of adults. It is secreted by the pituitary gland in response to exercise, deep sleep, hypoglycemia, glucagon, insulin and vasopressin. It also stimulates the production of RNA, and is intimately connected with insulinism. If the pituitary gland secretes too little or too much hGH in the growth phase of life, dwarfism of gigantism will result, respectively. An excess of growth hormone ducring adulthood leads to acromegaly.

This test confirms hypopituitarism or hyperpituitarism so that therapy can be initiated as soon as possible. Challenge or stimulation tests are generally used to detect hGH deficiency and are more informative. Much controversy surrounds the use of the growth hormone stimulation tests and the diagnosis should be considered in the context of the clinical picture.

Reference Values

Normal

Men: <5ng/ml or 226 pmol/L

Women: <10ng/ml or 452 pmol/L

Children: 0-20 ng/ml or 0-904 pmol/L

Newborns: 5-40 ng/ml or 226-1808 pmol/L

Stimulation test (using arginine, glucagon or insulin)

>5 ng/ml or 226 pmol/L (rise from baseline)

>10ng/ml or 452 pmol/L peak response from baseline

Suppression test (using 100 g glucose)

0-2 ng/ml or 0-90 pmol/L or undetectable

Clinical Significance

Increased hGH levels are associated with the ffg conditions:

a. Pituitary gigantism

b. Acromegaly

c. Laron’s dwarfism (hGH resistant)

d. Ectopic GH secretion

e. Uncontrolled Diabetes Milletus

Decreased hGH levels are associated with the ffg conditions:

a. Pituitary dwarfism

b. Hypopituitarism

c. Adrenocortical hyperfunction

Interferring Factors

Increased levels are associated with the use of oral contraceptives, estrogens, arginine, glucagon, levadopa, low glucose and insulin.

Levels will rise to 15 times normal by the second day of starvation; levels also rise after deep sleep, stress, exercise and anorexia.

Decreased levels are associated with obesity and the use of corticosteroids.

Many drugs interfere with the results

Recently administered interfere with the test results

Growth hormone suppression

Also called glucose loading, the growth hormone suppression test evaluates excessive baseline levels of hGH from anterior pituitary gland. Normally glucose and fatty acid aoncentrations; in response, insulin secretion increases to counteract these effects.

Purpose

-To assess elevated baseline levels of hGH

-To confirm diagnosis of gigantism in children and acromegaly in adults and adolescents

Reference Values

Normally, glucose suppresses hGH ti levels ranging from undetectable to 3 ng/ml(SI, 3 ug/L) in 30mins to 2hrs.

Abnormal findings

In a patient with active acromegaly, elevated baseline levels of hGH (5 ng/ml) aren’t suppressed to less than 5ng/ml during the test. Unchanged or rising hGH levels in response to glucose loading indicate hGH hypersecretion and may confirm suspected acromegaly and gigantism. This response may be verified the test after a 1-day rest.

Interfering factors

Failure to observe pretest restrictions

Hemolysis due to rough handling of the sample

Corticosteroids and phenothiazines such as chloropromazine

Radioactive scan performed within 1week before the test

Delay in sending the specimen to laboratory

References

John Bernard Henry 19^th edition pages 323-328

Clinical Chemistry by Michael Bishop pages 402-403

A manual of laboratory and diagnosis tests 7^th edition by frances fischbach pages 369-371

http://en.wikipedia.org/wiki/Growth_hormone#Functions_of_GH

See Picture 1 at:http://www.faqs.org/health/Body-by-Design-V1/The-Endocrine-System.htmll

See Picture 2 at: http://education.uncc.edu

See Picture 3 at: http://copland.udel.edu/~jwhite/dwarfism2.html

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Welcome

2009-05-26T00:17:00.000-07:00

Hi, I'm Kim Andrew, welcome to my blog.