endocrinology
DESCRIPTION
EndocrinologyTRANSCRIPT
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 lobe), which constitutes 80% of
the pituitary
2- The NEUROhypophysis or (posterior lobe), which is t h e s t o r a g e
s i t e for hormones produced by the neurosecretory neurons ( s u p r a o p t i c a n d p a r a v e n t r i c u l a r n u c l e i ) 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 h y p o t h a l a m u s (by the neurosecretory neurons ( s u p r a o p t i c
a n d p a r a v e n t r i c u l a r n u c l e i ) )
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 stimu-latory 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
HormoneSymbol
(s)Structure Target Effect
Adrenocorticotr
opic hormoneACTH Polypeptide Adrenal gland
Secretion
of glucocorticoid, mineralocorticoidand
androgens
Beta-endorphin Polypeptide Opioid receptor Inhibit perception of pain
Thyroid-
stimulating
hormone
TSH Glycoprotein Thyroid gland Secretion of thyroid hormones
Follicle-
stimulating
hormone
FSH Glycoprotein Gonads Growth of reproductive system
Luteinizing
hormone
LH,
ICSHGlycoprotein Gonads Sex hormone production
Growth
hormone
GH,
STHPolypeptide Liver, adipose tissue
Promotes
growth; lipid and carbohydrat
e metabolism
Prolactin PRL PolypeptideOvaries, mammary
glands
Secretion
of estrogens/progesterone; mil
kproduction
Leptin - PolypeptideCorticotrophic an
dThyrotrophic cellsTSH and ACTH secretion
Hormones OF THE Posterior PITUITARY (neurohypophysis)
HormoneSymbol(
s)Main targets Effect Source
Oxytocin OTUterus,mammary
glands
Uterine
contractions; lactati
on
supraoptic an
dparaventricular nuclei
ADH
(Vasopressin) VP, AVP,
ADH
Kidneys o
rArterioles
Stimulates water
retention; raises
blood pressure by
contracting
arterioles, induces
male aggression
supraoptic an
dparaventricular nuclei
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
Prolactin 50–60%
Growth hormone (GH) 15–20%
ACTH 10–15%
Gonadotroph 10–15%
Hyperprolactinemia
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 i s e r e c t i l e d y s f u n c t i o n a n d d e c r e a s e d l i b i d o .Prolactinomas : Autonomous production of prolactin occurs with pituitary adenomas Prolactinomas (Hyperprolactinemia) the most common functioning pituitary adenomas, accounting for 60% of all pituitary tumorsThey 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- pregnancy2- early nursing3- Hypoglycemia4- Seizure5- Exercise6- Stress7- Sleep8- Cirrhosis9- nipple stimulation10- Chronic renal failure (due to PRL clearance).11- Acromegaly
- Hyperprolactinemia can also occur with decreased inhibitory action of dopamine1- The use of drugs that block dopamine synthesis (phenothiazines, metoclopramide ) 2- dopamine-depleting agents (-methyldopa, reserpine)3- Tricyclic antidepressants4- Narcotics , cocaine5- 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 mengalactorrhea, menstrual abnormalities amenorrhea/oligomenorrhea, osteopenia and osteoporosis in long-standing cases, infertility, and gynecomastia
erectile dysfunction, decreased libido (most common ) hypogonadism , gynecomastia , and infertility
In both may be 1- Hemianopia (more in men due to the size of the tumor
2- Because of hypoestrogenism and hypoandrogenism, hyperprolactinemia can lead to osteoporosis3-
*# Women are detected earlier because of menstrual symptoms. Hence, microadenomas are more common in women
Diagnosis. At first Time exclude 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.
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 o n l y f o r a d e n o m a s n o t r e s p o n s i v e t o c a b e r g o l i n e o r b r o m o c r i p t i n e , or i f t h e t u m o r i s a ss o c i a t e d w i t h s i g n i f i c a n t c o m p r e ss i v e n e u r o l o g i c e f f e c t s .
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 if drug therapy and surgery are ineffective in reducing tumor size and prolactin levels
Notes 1- The most common presenting symptom in men is erectile dysfunction and decreased libido.
2- The Most common adenoma of the Pituitary is Hyperprolactinemia 60 %
3- The most common presenting symptom in Women are galactorrhea (58%), oligomenorrhea (58%)
4- 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.