Prolactinoma
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Prolactinoma
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Amenorrhea
pituitary prolactinomas p. 333
Galactorrhea
pituitary prolactinomas p. 333
Hypogonadism
pituitary prolactinomas p. 333
Osteoporosis p. 467
pituitary prolactinomas p. 333
Pituitary prolactinomas p. 333
Prolactinomas
dopamine agonists for p. 332
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With prolactinoma, prolactin refers to the endocrine hormone secreted by the pituitary gland and -oma refers to a tumor.
So a prolactinoma is a benign tumor, or adenoma, of the pituitary gland that secretes excess prolactin.
Normally, the pituitary is a pea-sized gland, hanging by a stalk from the base of the brain.
It sits just behind the eyes near something called the optic chiasm, which is where the optic nerves cross.
The anterior pituitary, which is the front of the pituitary gland, contains a few different types of cells, and each of which secretes a different hormone.
One group of cells in the anterior pituitary are called lactotrophs and they secrete prolactin.
Prolactin stimulates breast milk production.
Another group of cells are the gonadotrophs and they secrete two gonadotropic hormones - luteinizing hormone, or LH, and follicle-stimulating hormone, or FSH, both of which stimulate the ovaries in women which make estrogen and stimulate the testes in men which make testosterone.
Prolactin release is controlled by something called the hypothalamus, which is a structure at the base of the brain just above the pituitary gland.
It makes two key hormones, thyrotropin-releasing hormone which increases prolactin release, and dopamine, which inhibits the prolactin release and actually overrides the stimulatory effect of thyrotropin-releasing hormone.
That’s why dopamine is known as prolactin-inhibiting factor, and why it’s constantly released to prevent prolactin release in anyone that’s not pregnant.
High levels of prolactin in the blood sends a negative feedback signal to the hypothalamus, making it release more dopamine which then decreases prolactin levels.
High levels of prolactin can also signal the hypothalamus to decrease the secretion of gonadotropin releasing hormone or GnRH.
Gonadotropin releasing hormone acts on the anterior pituitary to make follicle stimulating hormone and luteinizing hormone or FSH and LH.
Now, during pregnancy the anterior pituitary gland releases prolactin and the placenta releases human placental lactogen and progesterone, and all three of these hormones stimulate the growth of more glandular tissue in the breast to produce milk.
Summary
A prolactinoma is a benign pituitary gland tumor that produces high levels of the hormone prolactin. Prolactin then suppresses the gonadotropin-releasing hormone resulting in symptoms like amenorrhea, galactorrhea, hypogonadism, gynecomastia, and erectile dysfunction in males. Treatment involves the use of dopamine agonist agents like bromocriptine which reduces the size of the tumor and lowers prolactin levels. In some cases, surgery or radiation therapy may also be required.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
- "Potential for long-term remission of microprolactinoma after withdrawal of dopamine-agonist therapy" Nature Clinical Practice Endocrinology & Metabolism (2006)
- "Demographic differences in incidence for pituitary adenoma" Pituitary (2010)
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