Download - Case File Hyperprolactinemia
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Case File
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Case # 14
A 30-year-old parous woman notes a watery breast
discharge of 6 months duration. Her menses havebeen somewhat irregular. She denies a family history
of breast cancer. The patient had been treated
previously with radioactive iodine for Graves disease.
Currently, she is not taking any medications. Onexamination, she appears alert and in good health. The
blood pressure (BP) is 120/80 mm Hg, and heart rate
(HR) is 80 beats per minute (bpm). The breasts are
symmetric and without masses. No skin retraction is
noted. A white discharge can be expressed from both
breasts. No adenopathy is appreciated. The pregnancy
test is negative.
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Our Approach to patient
What is the most likely diagnosis? What is your next step?
What is the likely mechanism for this
disorder?
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Summary:
A 30-year-old parous woman withirregular menses notes a watery
breast discharge of 6 months
duration. She had been treatedpreviously with radioactive iodine for
Graves disease. The pregnancy test
is negative.
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Most likely diagnosis:.
Next step:
Likely mechanism:
Most likely diagnosis:. Galactorrhea due to
hypothyroidismNext step: Check serum prolactin
and TSH levels.
Likely mechanism: Hypothyroidism is associated with anelevated thyroid releasing hormone
(TRH) level, which acts as a prolactin-
releasing hormone.
The hyperprolactinemia then induces
the galactorrhea.
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Hyperprolactinemia
Levels of circulatingprolactin above normal(>20 to 25 ng/mL) that can cause
galactorrhea or amenorrhea or both.
The optimal time to obtain a blood sample
for assay to diagnose is during the
midmorning hours.
Reference range
Female - gravid/nonlactatin : 2-29 ng/ml Gravid : 10-29 ng/ml
Male : 2-18 ng/ml
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Prolactin
Polypeptide hormone Contains 198 amino acids
MW of 22,000 daltons.
Different molecular sizes: Monomeric(small): 22,000 daltons
Polymeric(big): 50,000 daltons
Larger polymeric(big-big): > 100,000 daltons
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FORMS
1. Larger forms - contain added sugar moieties
(glycosylation) which decreases biologic
activity.
2. Small form(80%) - biologically active
3. Polymeric forms - have reduced biologic
activity and reduced binding to mammary
tissue membranes.
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Synthesized and stored in the pituitary gland
in chromophobe cells (lactotrophs),which arelocated mainly in the lateral areas of the gland
Encoded by its gene (10 kb) on chromosome 6
Prolactin9
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At the molecular level, it is stimulated and
suppressed by multiple factors.
Thyroid-releasing hormone(TRH) - Principal
stimulating factor
Dopamine- Major inhibiting factor
Estrogen - Enhances the effects of TRH and
inhibits the effects of dopamine
Galanin - May also mediate a potential direct effect
Prolactin10
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In addition, PRL is synthesized in decidualized
stroma of endometrial tissue.
From these tissues PRL is secreted into the
circulation and, in the event of pregnancy, intothe amniotic fluid.
The control of decidual PRL is different from
that of the pituitary and does not respond to
dopamine.
Prolactin11
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Normally present in measurable amounts in
serum
Mean levels of about 8 ng/mL in adult women
Circulates in an unbound form
20-minute half-life
Cleared by the liverand kidneys
Prolactin12
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Main function is to stimulate the growth of
mammary tissue as well as to produce andsecrete milk into the alveoli(mammogenic and
lactogenic).
Specific receptors for PRL are present in the
plasma membrane of mammary cells as well
as many other tissues
Prolactin13
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TRANSITIONAL PAGE
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