3. IntroductionIntroduction
Human PRL is a single-chain polypeptide of
199 amino acids. It has a molecular weight of
23 kDa.
Prolactin is synthesized in and secreted from
specialized cells of the anterior pituitary
gland, the lactotroph cells.
The pituitary gland (also called the master
gland) is an endocrine gland about the size of
a pea (weighing 0.5 g) and located at the base
of the brain (just below the hypothalamus).
The pituiary gland has two parts – the anterior
lobe and posterior lobe – that have two
seperate functions.
The pituitary gland secrets hormones
regulating homeostasis, including tropic
hormones that stimulate other endocrine
glands.
6. FunctionFunction
o
PRL is responsible of:
Primarily; initiating and sustaining lactation and stimulation of breast development along with
Estrogen during pregnancy.
o
Other functions of PRL:
Reproductive; inhibition of ovulation by decreasing secretion of LH and FSH during pregnancy.
Regulation of immune system;by stimulating T cell functions.
Osmoregulation; transporting fluid, Na, Cl and Ca across epithelial intestinal membrane and
promoting Na, K and water retention in the kidney.
Metabolism; essential in fat cell production, differentiation and regulation.
7. Regulation of secretion
o Breast feeding is the major stimulus of prolactin production.
o Triggered by the prolactin releasing hormone (PRH)
o Inhibited by prolactin inhibiting hormone (PIH), dopamine,
acting on the D2 receptors present on the lactotroph cells
In males, the influence of PIH predominates.
In females, PRL levels increase and decrease in accordance with
estrogen blood levels;
-Low estrogen levels stimulate PIH release.
-High estrogen levels promote release of PRH and thus PRL.
o Blood levels increase towards the end of the pregnancy.
o When the mother no longer needs to produce milk, dopamine
inhibits prolactin by signaling the hypothalamus to stop.
8. Causes and Symptoms of HypoprolactinaemiaCauses and Symptoms of Hypoprolactinaemia
Decreased PRL hormone secretion by the anterior pituitary gland
Common causes of Hypoprolactinaemia:
o Sheehan'ssyndrome (caused by ischaemic necrosis of the pituitary gland due to blood loss during or after child
birth)
o Hypopituitarism
o Excess dopamine
o Autoimmune disease
o Growth hormone deficiency
o Head injury
o Infection (e.g. Tuberculosis)
Symptoms:
o Ovarian diseases, delayed puberty and infertility.
o Impotence and abnormal spermatogenesis.
9. Causes and symptoms of HyperprolactinaemiaCauses and symptoms of Hyperprolactinaemia
Increased PRL hormone secretion by the anterior
piruitary gland
Common causes of Hyperprolactinaemia
Stress
Medications e.g. Antipsychotic drugs
Primary hypothyroidim: PRL is stimulated by
the increase of TRH.
Pituitary gland tumours
Prolactinoma: a non-cancerous tumour of the
pituitary cell secreting PRL.
Idiopathic hypersecretion: e.g. due to impaired
secretion of dopamine
Other: chest wall lesions and chronic renal
failure.
Symptoms:
Women:
Oligomenorrhoea
Amenorrhoea
Galactorrhoea
Infertility
Hirsutim
Osteoporosis
Men (late onset):
Gynaecomastia.
Impotence.
Osteoporosis
In both sexes, tumour mass effects may cause visual-
field defects and headache.
10. Diagnosis and TreatmentDiagnosis and Treatment
Diagnosis:
o
History (medications, oligomenorrhoea,
hirsutim)
o
Physical examination ( galactorrhoea)
Laboratory
Pregnancy Test
Prolactin
Macroprolactin (inactive, large complex of
serum prolactin with an IgG antibody)
TSH, Free T4
U&Es
Tes, LH, and FSH
o
MRI scan ( prolactinaemia)
o
Visual field tests (optic nerve)
Treatment:
o
Hyper prolactinaemia: dopamine agonists
(e.g. Bromocriptine or Cabergoline)
o
Surgery removal and/or radiation therapy
(large pituitary tumours)
o
Tyroid abnormalities: thyroid hormone
replacement ( e.g. levothyroxine)
o
Ovarian insufficiency: hormonal therapy
(e.g. Estrogens and Progestins)
11. Case studyCase study
A 56 years old male who was recently admitted to A&E for fall-related injuries (cracked
right sided rib and right knee injury)
In June, the pt was referred to the endocrine clinic due to the detection of an adrenal incidentaloma.
Other clinical history include atrial fibrillation and pleural thickening.
Lab investigations (12/09/2016)
? cause
Test Reference
range
Result
Prolactin 73-407 mU/L >42000
Tes Male >50 yrs
7-30 nmol/L
3.0
TSH 0.35-5.0 mU/L 4.64
FT4 9-19 pmol/L 12
LH 2-10 IU/L 2.0
FSH 1-5 IU/L 3.0
12. ProlactinomaProlactinoma
MRI scan was performed to confirm or rule out prolactinoma.
The radiology report:
”46 x 37 x 35 mm pituitary tumour in keeping with pituitary macroadenoma.
Encroachment of clivus, sphenoid sinus, left-sided optic pathways and
cavernous sinus bilaterally.”
13. References
Freeman M. et al(2000) Prolactin:Structure, Function, and Regulation of Secretion, American Physiological Society [online]
http://physrev.physiology.org/content/80/4/1523.long
Ugwa E. et al (2016) Assessment of serum prolactin levels in among infertile women with galactorrhea attending a
gyneclogical clinic North-West Nigeria, Nigerian Medical Journal, [online]
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4924401/
Nevels R. et al (2016) Paroxetine- The Antidepressant from Hell? Probably Not, But Caution Required, Psychopharmacology
Bulletin, [online] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5044489/
Nessar A. (2010) Clinical Biochemistry. New York. Oxford University Press.
Besser G.and Thorner M. (1994) Clinal Endocrinology. London. Times Mirror International.
Video: https://www.youtube.com/watch?v=PHjwymgSTrE
