Endocrine Physiology Flashcards
Describe the Posterior Pituitary (derivative, composition, and AKA)
- Derived embryonically from an outgrowth of the brain
- Composed of nervous tissue
- Also called the neurohypophysis
Describe the Anterior Pituitary (derivative, composition, and AKA)
- Derived embryonically from an outpouching that buds off from the roof of the mouth
- Composed of glandular tissue
- Also called the adenohypophysis
Describe the hormones released from the Posterior vs. Anterior Pituitary
Posterior:
- Oxytocin –> Uterine muscles + mammary glands
- ADH –> Kidney tubes
Anterior:
- TSH
- ACTH
- FSH + LH
- GH
- PRL
- Endorphins
Describe the Posterior Pituitary
- Neuroendocrine system
- Composed of neurosecretory cells whose cell bodies lie in the hypothalamus.
- Infundibular stalk arises out of the median eminence
- Connects the hypothalamus and posterior pituitary.
- Axons from the hypothalamus terminate on capillaries in the posterior pituitary.
- Functionally, the posterior pituitary is an extension of hypothalamus
Describe the Anterior Pituitary
Unlike the posterior pituitary, which releases hormones synthesized by the hypothalamus, the anterior pituitary synthesizes its own hormones.
The portal system carries neurohormones from the hypothalamus to anterior pituitary to control its secretions.
What are the Anterior Pituitary Cell Types
- GH secreted by somatotrophs
- PRL secreted by lactotrophs
- ACTH secreted by corticotrophs
- TSH secreted by thyrotrophs
- LH, FSH secreted by gonadotrophs
Anterior Pituitary Hormones
TSH, ACTH, FSH and LH are all tropic hormones:
- they regulate the secretion of another specific endocrine gland
- FSH and LH are referred to as gonadotropins - they control secretions of the sex glands
An anterior pituitary hormone may be regulated by a stimulatory and an inhibitory hypothalamic hormone (ex. GH, TSH, PRL)
Effects of Anterior Pituitary Hormones
- Usually, the effect of the stimulatory hormone predominates.
- Except, PRL (effect of Dopamine»_space;> TRH)
- So, if pituitary is separated from hypothalamus, PRL levels increase, while all others decrease
What happens when one gets a Pituitary Adenoma (noncancerous tumors that occur in the pituitary gland)?
Prolactin-secreting pituitary adenomas are the most common type!… Secrete more PRL
What is the primary function of PRL?
-Major hormone responsible for milk production
Where is PRL synthesized/secreted?
-Synthesized/secreted by lactotrophs in pituitary
What controls the release of PRL?
Release is controlled by two hormones:
Dopamine (inhibitory)
Thyroid releasing hormone (stimulating)
What is the Function of PRL?
- Growth of breasts
- Lactogenesis: synthesis of enzymes involved in milk production
- Inhibition of ovulation: inhibits GnRH release and thus, LH release
What are the Clinical Features of Prolactinoma in young menstruating women and men/postmenopausal women?
1) Young menstruating women
- Irregular menses (amenorrhea, oligomenorrhea, delayed menarche)
- Infertility
- Galactorrhea (30-80% of women)
- Hirsutism
- Typically microadenomas
2) Men and postmenopausal women
- Decreased libido (80%)
- Impotence (full or partial)
- Hypogonadism
- Galactorrhea (20-30%)
- Visual field abnormalities
- Extraoccular muscle palsies
- Headaches
- Typically macroadenomas
What are the Clinical Features of Prolactin-Secreting Pituitary Adenomas?
1) Prolactin microadenoma
- Usually less than 1 cm in diameter
- Only presenting symptoms may be amenorrhea-galactorrhea syndrome
2) Larger pituitary adenomas
- May have intracranial symptoms: bitemporal hemianopia, retro-orbital headaches
- May also have pituitary failure with thyroid, gonadal, and adrenal insufficiency