Wednesday, January 23, 2008

Prolactin in MRCP

Prolactin in MRCP

I always enjoyed studying endocrinology during my medical school time. One of my old professors said, endocrinology is straight forward and logical. Our body is designed in a way when our hormone level is high, there will be a negative feedback and vice versa. Our bodies try to maintain a normal level of all hormones so that we can function normally.

A trick to remember when you study endocrinology, you must understand normal physiology so that you can understand each hormone clearly and not just memorize them by hard.

OK, today, we will start to learn the first hormone- prolactin. Why prolactin?It is rather interesting that we know prolactin is important for females because it helps in milk production but its function in males remains a mystery!

I think there are a few important facts about prolactin that always asked in your MRCP!

Fact 1:

All hormones in pituitary glands are up regulated by another hormone in hypothalamus ( positive feedback) except prolactin. This means that prolactin production will be inhibited by another hormone prolactin inhibiting hormone ( PIH) from hypothalamus. Remember that PIH is dopamine, therefore your dopamine agonist such as bromocriptine is used to suppress prolactin and thus milk production. ( And also remember that due to its dopaminergic effects, bromocriptine is used in Parkinson’s disease).

Whereas drugs which as anti-dopamin effect such as metoclopramide is used to stimulate prolactin production and it is always used in O+G for post partum mothers if they have problems in milk production.

Fact 2:

You do not believe it, prolactin is a stress hormone. As a medical student, I always do not understand why God created prolactin as stress hormone. Anyway, prolactin level can be measured if you want to differentiate a true seizure from pseudo-seizure because its level is high after an epileptic fit.

Fact 3:

When there is a non-secreting tumour in pituitary causing damage to the stalk, you anticipate secretion of all hormones from pituitary to be reduced ( because positive feedback from hypothalamus) but prolactin level is high because there is no negative feedback from hypothalamus.

Fact 4:

One of the commonest causes of hyperprolactinoma and galactorrhoea is drug-induced and it is due to Phenothiazines!!

Friday, January 11, 2008

Benign Intracranial Hypertension in MRCP

Benign Intracranial Hypertension in MRCP

I always remember that benign intracranial hypertension is a popular topic in MRCP Part 1 and 2. Recently, my wife was studying her FRACGP and I noticed that BIH is one the hottest topics as well.

Since this illness is so popular and important, I think we should spend sometime talking about BIH today.

OK, why we say intracranial hypertension is benign?? When there is intracranial hypertension, we anticipate there will be some problems inside our craniums, however, if there is presence of intracranial hypertension without any obvious intracranial mass or enlargement of ventricles or hydrocephalus, we term the illness as BENIGN ( it won’t kill you!!) intracranial hypertension.

There are a few facts to remember for BIH,

Fact 1:



Remember that majority of patients are young female who are obese and usually in your MRCP, they will give you an example of an obese lady with acne. Why acne?? I always wondering when I was a medical student. After struggling for many years, I finally understood this. The reasons are, some anti- acne actually cause BIH such as teteracycline, Vitamin A and drugs that can precipitate acne formation such as steroid also lead to BIH!!

Fact 2:

Although we were taught that papilloedema is an emergency if patient has headache. Remember that patient with BIH has headache and papilloedema ( although rarely they might have blurring of vision and seizure) but it is benign and the brain imaging and CSF are normal.

Fact 3:

Since patient with BIH is always a young female patient, you must put sagittal sinus thrombosis as your differential diagnosis. This is because you also anticipate young ladies are prone to get autoimmune disease especially SLE and they are usually on oral contraceptive pills and these put the ladies at risk of developing sagittal sinus thrombosis.


Fact 4:

Treatment is easy, stop the drug and weight reduction but you may use loop diuretics or acetazolamide.



Example of question:



A 22-year-old obese woman presented with an 8-week history of headaches, pulsatile tinnitus and transient visual loss on standing lasting a few seconds. She had otherwise been well with no history of note. She took the oral contraceptive pill and had been taking this for the last 6 months and used salbutamol inhalers on an occasional basis for her asthma which she had from childhood. She also took vitamin Asupplements which she bought over the counter for her general health. On examination, the only abnormality of note was bilateral papilloedema. MRI brain and MR Venogram are normal. Lumbar puncture showed an opening pressure of 38, normal protein, glucose, and cells.. What is the most likely diagnosis?



1 )Herpes simplex encephalitis

2 )Intracranial hypertension secondary to vitamin A

3 )Malignant meningitis

4 )Sagittal sinus thrombosis secondary to OCP

5 )Sagittal sinus thrombosis secondary to SLE

Tuesday, January 08, 2008


Drug in MRCP-Phenytoin

Although some of you may be not so familiar about phenytoin especially for those who are practicing medicine in developed countries. I think this is because there are so many new antiepileptic drugs available in the market now.

Actually, phenytoin is the oldest non-sedative antiepileptic drug introduced in 1938!!
I think it is not so important for you to understand how phenytoin acts because I myself never understand it when I was a medical student myself many years ago.

In MRCP examination, there are a few important facts that you must always remember.

Fact 1 : Drug metabolism/binding

Remember that phenytoin is mainly bound to protein. Therefore, when there is hypoalbuminemia, there is decreased protein binding- results in a decrease in total plasma concentration of drug but not the free concentration.

Therefore a lot of doctors tend to increase the drug dosage to maintain total drug levels in the therapeutic range- leading to toxicity.

Besides that remember that hepatic enzyme induction and inhibition also alter its drug level.

Although phenytoin is mainly metabolized in liver, its metabolites are excreted in kidney, therefore, renal failure may precipitate toxicity.

Fact 2: Side effects

As I remember as a medical student, there are two interesting side effects of phenytoin- gum hypertrophy ( Look out the photo at http://www.passpaces.com/ ) and generalized lymphadenopathy. However, remember that acute toxicity of phenytoin also leads to cerebellar signs!!

Fact 3: Cardiac complications

Since phenytoin alters Na, K and calcium conductance, it can cause cardiac arrhythmia, therefore always put patient on cardiac monitor if you suspect toxicity.

Also remember that chronic use of phenytoin can lead to Vitamin D metabolism abnormalities and osteomalacia.