Endocrine disorders 1 of 2 Flashcards
1) where is prolactin secreted from in the body?
2) what stimulates the production of HP-Prolactin and what effect does it have on the body?
1) the pituitary gland in response to eating, mating, estrogen treatment, ovulation and suckling stimulus
2) Prolactin released from the pituitary gland stimulates mammary gland development: DNA synthesis, epithelial cell proliferation, this leads to synthesis lactose and free fatty acids
3) role is to help initiate and maintain breast milk production in pregnant and nursing women.
describe the effects of the Hypthalamic-Pituitary-Testicular Axis
1) The hypothalamus produces Gonadotropin-releasing hormone (GnRH). This stimulates the gonadotroph cells in the anterior ptuitary to produce FSH (follicle-stimulating hormone) and LH (luteinizing hormone)
2) FSH acts on spermatogenic cells together with testosterone to stimulate sperm production
3) LH also acts mainly on testis and stimulates testosterone secretion
4) leydig cells secrete testosterone . the testosterone feeds back on both the pituitary and the hypothalamus and prevents the production GnRH and reduces the production of LH and FSH - negative feedback loop
5) Androgen-binding protein (ABP) produced by the Sertoli cells in the testis binds specifically to testosterone. ABP feeds back in a negative manner to reduce FSH production
describe the effects of the H-P-Ovary axis
1) GnRH stimulates the production of FSH and LH
2) FSH stimulates the growth of ovaries
3) LH stimulates ovulation
4) once ovulation occurs the tissue reorganises itself into a corpus luteum. during the first half of the cycle up till ovulation you get the production of estrogens which feed back in a negative manner on the anterior pituitary and hypothalamus
6) in the second half of the cycle you get poroduction of progesterone from the corpus luteum
what is the role of the HPT axis (Hypothalamus/Pituitary/Thyroid)?
1) hypothalamus produces thyrotropin Releasing Hormone (TRH)
2) TRH stimulates anterior pituitary to produce thyroid Stimulating Hormone (TSH)
3) TSH is then released into the circulation and acts on the thyroid gland to produce two hormones T3 and T4
4) T3 and T4 feedback on both the anterior pituitary and hypothalamus ( negative feedback loop). TSH will also negatively feedsback on the hypothalamus as well.
outline the effects of Thyroid Hormone (T3 and T4) on the body
1) Increases basal metabolic rate (BMR): Raised O2 consumption, CO2 production, heat production
2) Cardiovascular system : Increases heart rate and force of contraction
3) Nervous system: Increases activity of sympathetic nervous system . Enhances the sensitivity to catecholamines
4) Growth and maturation (essential): Embryo development, CNS development, Linear growth (promotes effects of growth hormone)
which two factors control the production of Growth hormone?
which cells produce growth hormone?
1) Growth hormone–releasing hormone (GHRH) has a positive effect.
2) Somatostatin has a negative effect on GH production.
3) both these hormones are produced in the hypothalamus and feed down to the somatotroph cells in the anterior pituitary.
4) in response the cells release growth hormone (GH) in response to Growth hormone releasing hormone (GHRH) or are inhibited by GHIH (somatostatin)
what is the main role of GH?
1) Promotes growth of bone and muscles
2) Has metabolic effects on most tissues
the actions of GH on target tissues can be both direct and indirect. describe the direct actions
Generally antagonistic to insulin → “diabetogenic effects”.
1) Reduce glucose transport into cells →increase plasma glucose
2) Increase lipolysis → increase plasma fatty acids
3) Increased amino acid transport into muscle → increase muscle growth and decrease plasma AA, urea
Describe the indirect effects of growth hormone.
1) Indirect actions mediated by insulin-like growth factors (IGFs= somatomedins)
2) GH promotes IGF production by liver
3) IGF promotes:
- Linear growth of bones
- Growth/cell proliferation of soft tissues, viscera
outline the disorders which can occur with regards to GH secretion
1) Hypopituitaryism: too little GH in childhood leads to dwarfism
2) GH-secreting pituitary tumour: GH excess
in young, leads to giantism
- in adult: acromegaly- thickening of bones and soft tissues and coarsening of features
1) how do you treat Growth hormone (GH) deficiency in childhood?
2) how do you treat Gigantism?
1) GH deficiency in childhood leads to very short stature. Treatment: Replacement therapy with human GH. Recombinant protein – Somatropin given by injection
2) Gigantism cause by GH over-secretion in childhood (prepuberty). This leads to very tall stature. Treatment: Surgical removal of pituitary and/or suppression of GH secretion using somatostatin analogues lanreotide and octreotide. this slows down the production of GH
what is Acromegaly and how is it treated?
1) Growth hormone over-secretion in adulthood.: leads to thickening of bone, distortion of facial features.
2) Treatment : Surgical removal of pituitary and/or somatostatin analogues or GH receptor antagonist – Pegvisomant.
Explain the cause of disorders related to the action of GH?
1) GH receptor: Identified in known target tissues (eg: liver, muscle, adipose tissue)
2) Laron syndrome: levels of GH are either normal or much higher, but the levels of Serum IGF-1 undetectable
- is a condition that occurs when the body is unable to utilize growth hormone.
3) may be Caused by mutation in GH receptor
how can Laron syndrome be treated?
Can be treated with IGF-1
