By The Name Of The God
Internal medicine
Endocrinology
DISEASES OF THE PITUITARY GLAND
The pituitary is divided into 2 lobes—
1 The Adenohypophysis or (anterior
the pituitary
lobe), which constitutes 80% of
2 The NEUROhypophysis or (posterior lobe), which is the storage
site for hormones produced by the neurosecretory neurons (supraoptic
and paraventricular nuclei) within the hypothalamus. The 2 hormones
stored in the are ADH (antidiuretic hormone or vasopressin)
and oxytocin
(focus ) The hormones Of posterior lobe (ADH and oxytocin)
produced by hypothalamus (by the neurosecretory neurons
(supraoptic and paraventricular nuclei) )
The hypothalamus regulates the release of hormones from the anterior pituitary
by different hypothalamic releasing and inhibiting hormones (hypothalamic–
pituitary axis)
- Each pituitary hormone stimulates release of the active hormone from the final
target gland. The active hormones then inhibit release of releasing factors and stimulatory hormones from the hypothalamus and pituitary gland, respectively. This is
feedback inhibition (e.x ACTH go to adrenal stimulates to produced cortisol and
cortisol go back to hypothalamus and stops releasing the ACTH it’s called
((Feedback ))
We use this physiology to screen and diagnose these
diseases
Hormones OF THE ANTERIOR PITUITARY
Symbol
Hormone
(s)
Adrenocorticotr
opic hormone
Structure
Target
Effect
Secretion
ACTH
Polypeptide
Adrenal gland
of glucocorticoid, mineralocorticoidand
androgens
Beta-endorphin
Polypeptide
Opioid receptor
Inhibit perception of pain
TSH
Glycoprotein
Thyroid gland
Secretion of thyroid hormones
FSH
Glycoprotein
Gonads
Growth of reproductive system
Glycoprotein
Gonads
Sex hormone production
Thyroidstimulating
hormone
Folliclestimulating
hormone
Luteinizing
LH,
hormone
ICSH
Growth
GH,
hormone
STH
Prolactin
Leptin
PRL
-
Promotes
Polypeptide
Liver, adipose tissue
growth; lipid and carbohydratemetabolis
m
Polypeptide
Polypeptide
Ovaries, mammary
glands
Corticotrophic andThyr
otrophic cells
Secretion
of estrogens/progesterone; milkproducti
on
TSH and ACTH secretion
Hormones OF THE Posterior PITUITARY (neurohypophysis)
Symbol(
Hormone
Main targets
s)
Oxytocin
OT
Uterus,mammary
glands
Effect
Uterine
contractions; lactati
on
Source
supraoptic andparaventricu
lar nuclei
Stimulates water
retention; raises
ADH
(Vasopressin)
VP, AVP,
Kidneys orArteriol
blood pressure by
supraoptic andparaventricu
ADH
es
contracting
lar nuclei
arterioles, induces
male aggression
These hormones produced in supraoptic and paraventricular nuclei and storage
an d secreted from Posterior Pituitary (neurohypophysis)
DISEASES OF THE ANTERIOR PITUITARY
Microadenomas are defined as tumors <1 cm in diameter.
Macroadenomas are tumors >1 cm in diameter.
Microadenomas are more common than macroadenomas
Larger tumors can occasionally compress the optic chiasm and can cause visual deficits.
Pituitary Adenomas by Function
Hyperprolactinemia
Prolactin
50–60%
Growth hormone (GH)
15–20%
ACTH
10–15%
Gonadotroph
10–15%
Definition. Excess prolactin secretion is a common clinical problem in women and causes the
syndrome of galactorrhea-amenorrhea. The amenorrhea appears to be caused by inhibition of
hypothalamic release of gonadotropin-releasing hormone (GnRH) with a decrease in
luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) secretion. Prolactin inhibits
the LH surge that causes ovulation. The LH/FSH-producing cells are not destroyed, just
suppressed. Although hyperprolactinemia is also seen in men, gynecomastia and especially
galactorrhea are very rare.
The most common presenting symptom in men is erectile dysfunction and decreased
libido.
Prolactinomas : Autonomous production of prolactin occurs with pituitary adenomas
Prolactinomas (Hyperprolactinemia) the most common functioning pituitary adenomas,
accounting for 60% of all pituitary tumors
They are usually microadenomas when they occur in women and macroadenomas in men,
usually presenting with visual field deficits. (in women we will detected the adenoma early due to
the to many and clear symptoms )
-
Macroadenomas can obstruct the pituitary stalk, increasing prolactin release by blocking
dopamine transport from hypo-thalamus (stalk effect). Other examples are tumors, such as
craniopharyngioma, meningioma, and dysgerminoma; empty sella; and trauma .
Etiology :
- natural physiologic states :
1- pregnancy
2- early nursing
3- Hypoglycemia
4- Seizure
5- Exercise
6- Stress
7- Sleep
8- Cirrhosis
9- nipple stimulation
10- Chronic renal failure (due to PRL clearance).
11- Acromegaly
-
Hyperprolactinemia can also occur with decreased inhibitory action of dopamine
12345-
The use of drugs that block dopamine synthesis (phenothiazines, metoclopramide )
dopamine-depleting agents (-methyldopa, reserpine)
Tricyclic antidepressants
Narcotics , cocaine
SSRIs
Other
1- Primary hypothyroidism (resulting in an increase in thyrotropin-releasing hormone [TRH]) and
subsequently an increase in prolactin release.
Always check TSH in patients with elevated prolactin
Clinical.
women
galactorrhea, menstrual abnormalities
amenorrhea/oligomenorrhea, osteopenia and
osteoporosis in long-standing cases, infertility,
and gynecomastia
men
dysfunction, decreased libido (most
common ) hypogonadism , gynecomastia , and
infertility
erectile
In both may be
2-
1- Hemianopia (more in men due to the size of the tumor
Because of hypoestrogenism and hypoandrogenism, hyperprolactinemia can lead to osteoporosis
3-
*# Women are detected earlier because of menstrual symptoms. Hence, microadenomas are more
common in women
Diagnosis. At first Time e xc l ude states
-
Pregnancy by hCG
-
Hypothyroidism By TSH
-
Lactation
-
Medications
Before starting the work-up of hyperprolactinemia. Prolactinomas may secrete growth hormone (GH).
The normal values for prolactin are:
Males: 2 - 18 ng/mL.
Nonpregnant females: 2 - 29 ng/mL.
Pregnant women: 10 - 209 ng/mL.
o
o
o
Dx :1-
Prolactin levels >100 ng/mL suggest probable pituitary adenoma
in non-pregnant women
Usually with
-
-
Prolactin levels 100 ng/ml = tumor size 1 cm
Prolactin levels 200 ng/ml = tumor size 2 cm. etc.
** MRI PRL level >100 to 200 mg/L (normal <20 mg/L) in a nonpregnant woman indicates a need for an MRI
of the pituitary.
Management:
For Prolactinomas, initially treat with cabergoline or bromocriptine (a dopamine agonist), which
reduce prolactin levels in almost all hyperprolactinemic patients. Dopamine normally inhibits
prolactin release. Surgery is reserved only for adenomas not responsive to cabergoline or
bromocriptine, or if the tumor is associated with significant compressive neurologic effects.
Surgery is more effective for microadenomas than macroadenomas.
About 90% of patients treated with cabergoline have a drop in prolactin to <10% of pretreatment levels.
Radiation therapy is used
prolactin levels
if drug therapy and surgery are ineffective in reducing tumor size and
Notes
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The most common presenting symptom in men is erectile dysfunction and decreased libido.
The Most common adenoma of the Pituitary is Hyperprolactinemia 60 %
The most common presenting symptom in Women are galactorrhea (58%), oligomenorrhea (58%)
The Treatment Of choice of Hyperprolactinemia is Medical treatment by cabergoline(used mostly )
or bromocriptine .
5- Cabergoline is used more often than bromocriptine because of a better side-effect profile. It should
be considered the preferred medical treatment for galactorrhea.