HORMONES OF THE ENDOCRINE SYSTEM Flashcards
Synthesized in thyrotrophs
I. THYROID STIMULATING HORMONE
Composed of two non-covalently linked alpha & beta sub-units
I. THYROID STIMULATING HORMONE
a-unit is identical to
FSH, LH & hCG
B-unit attaches to
thyroid receptors
Significance of TSH:
- Stimulates growth and vasculature of the thyroid gland
- Uptake and organification of iodine
- Promotes release of stored thyroid hormones
Ultrasensitive method for TSH determination
Immunoradiometric assay (IRMA)
best thyroid function test
Immunoradiometric assay (IRMA)
Differentiate hypo vs hyperthyroidism
Immunoradiometric assay (IRMA)
LATS (long acting thyroid stimulating substance)
Immunoradiometric assay (IRMA)
detectable in the serum of thyrotoxic patients which imitates the biologic action of TSH
LATS (long acting thyroid stimulating substance)
GONADOTROPINS
LH
FSH
• Secreted by the gonadotropic cells
Luteinizing Hormone (LH) & Follicle-Stimulating Hormone(FSH)
• Control the FSH functional activity of gonads
Luteinizing Hormone (LH) & Follicle-Stimulating Hormone(FSH)
Promotes and maintains the 2nd portion of the menstrual cycle
LH in females
Cause release of ova from ovarian follicles
LH in females
Transformation of the follicle into the corpus luteum after ovulation
LH in females
Secretion of progesterone by the corpus luteum
LH in females
Responsible for production of testosterone by the Leydig cells of the testes
LH in males
Maturation of spermatozoa requires both
LH & FSH
Stimulates growth & maturation of ovarian follicles
FSH in females
Promote endometrial changes characteristics of the 1st portion of menstrual cycle
FSH in females
Promotes secretion of estrogen by maturing follicles (in the presence of LH)
FSH in females
Stimulates spermatogenesis
FSH in males
Stimulates testicular growth production of ABP (androgen binding protein) by the Sertoli cells
FSH in males
slight inc in FSH: stimulates devt of ovarian follicle
Follicular Phase
14th day: inc in LH and ESTROGEN (promotes and maintains ovulation of follicles)
Ovulatory Phase
Released ovum is passed thru fallopian tube to be ready for fertilization by the sperm
Ovulatory Phase
Follicle transforming to corpus luteum
Luteal Phase
inc PROGESTERONE
Luteal Phase
METHODS FOR DETERMINATION FOR TSH
Commercial RIA kits for both blood (serum or plasma) & urine samples
Because of episodic, circadian & cyclic variation in secretion of gonadotropins, clinical evaluation requires determinations in:
Pooled blood samples
Multiple serial blood samples
Timed sample of urine
collected in different time intervals, pulled together, measured as one
Pooled blood samples
now, after 1 hour, another 1 hour/ morning, afternoon, evening
Pooled blood samples
1-time testing (cheaper)
Pooled blood samples
collect sample w/ timed intervals
Multiple serial blood samples
tested each samples as collected
Multiple serial blood samples
serial blood collection and testing serial
Multiple serial blood samples
all blood samples tested (more expensive)
Multiple serial blood samples
more accurate - average of all results
Multiple serial blood samples
secreted by Luteotropin
II. PROLACTIN
: initiation and maintenance of lactation
Milk let down reflex
Physiologic increase seen during:
• Pregnancy • Lactation • Post pubertal women
• Promotes milk production following birth of an infant.
II. PROLACTIN
• The effect of PRL in males is less understood, although it may cause a
deficiency of male sex hormones.
PRL • main target tissue: [?] (production of milk)
breast
• Secreted in circadian fashion
• Increased during sleep
• Lowest at 10am to 12mm
• Secreted in pulsatile fashion
II. PROLACTIN
• 3 specimens taken at
20-30 minutes intervals
Conc varies throughout the day
pulsatile fashion
PRL Major circulating form:
non-glycosylated monomer
PRL Other forms:
• “Big” prolactin
• Macroprolactin (“big, big” prolactin)
Protein attached to a circulating protein
“Big” prolactin
coupled with immunoglobulin (usually IgG)
Macroprolactin (“big, big” prolactin)