Dynamic Endocrine Testing Flashcards
What gonadotropin and androgen levels can be presented with hypogonadotrophic hypogonadism, for men and women respectively?
Hypogonadotrophic hypogonadism:
Men: Low LH and Low Testosterone (reduced libido and muscle tone)
Women: Low FSH and Low Estrogen (irregular cycles and osteopenia)
List one example of a positive feedback mechanism in the endocrine system.
HIGH E2 levels in the late follicular phase can stimulate Activin which activate gonadotropins to secrete LH “LH surge before ovulation”.
Name at least 2 examples of negative feedback in the endocrine system.
- Low E2 levels lowers GnRH pulsatility which inhibits FSH.
- High Cortisol levels can negatively feedback CRH secretion.
- Thyroxine hormone can inhibit TSH (thyrotropin)
Describe an example of an autocrine feedback communication that occurs in the endocrine system.
Activin made by gonadotropes (in HIGH E2) can stimulate LH secretion from same gonadotropes in Anterior Pituitary.
Describe an example of a paracrine feedback communication in the endocrine system.
Theca cells stimulated by LH make androgens (such as Testosterone) that affect Granulosa cell function to produce more Estrogen (E2).
What are the 5 families of steroid hormones? Name the Bioactive (B) and weaker (I) hormones within each family.
“P-GAME”
- Progestins: Progesterone (B) and Pregnenolone (I)
- Glucocorticoids: Cortisol (B) and Cortisone (I)
- Androgens: Testosterone/DHT(B) and Androstenedione, DHEA-S (I)
- Mineralocorticoids: Aldosterone (B) and Corticosterone (I)
- Estrogens: Estradiol (B) and Estriol/Estrone (I)
What is the premise of Endocrine Dynamic Testing? How can this be used in the clinic?
Endocrine dynamic testing is a process of stimulation and suppression tests. This affects positive and negative feedback communication of the body, which can be useful for clinicians in diagnosing an endocrine disorder.
Describe what the GnRH stimulation test can be used for. What effect does this have on pre-pubescent children?
GnRH stimulates the secretion of LH > FSH from the anterior pituitary. Exogenous GnRH should have no effect on pre-pubescent children since the gonadotropes have not been activated yet. This can be used to test for central precocious puberty, if LH secretion is noted in a young child with such signs/symptoms.
What gonadotropin and androgen levels are expected in hypergonadotropic hypogonadism, in males and females respectively?
Hypergonadotropic hypogonadism:
Males: Low Testosterone and HIGH LH (reduced libido and muscle tone)
Females: Low Estrogen and HIGH FSH (irregular periods and less secondary characteristics)
In regards to hypogonadotrophic hypogonadism, what treatments can be given for the affected man? What of the affected woman?
A man with this condition can be given GnRH agonist or exogenous Testosterone. An affected woman can be provided E2/P4 hormone therapy.
How does Cushing’s Syndrome differ from Cushing’s Disease?
Cushing’s Syndrome describes any condition resulting in HIGH Cortisol levels (I.e. Cortisol secreting tumor, peripheral source). Cushing’s Disease is a neuroendocrine issue of Hypothalamic-pituitary origin.
How do hormone levels of Cushing’s Disease contrast from those of Cushing’s Syndrome?
Cushing’s Disease can present as high levels of CRH or ACTH along with Cortisol. This contrasts from Cushing’s Syndrome that only presents as HIGH Cortisol. Negative feedback prevents the trophic hormones from rising in the latter.
When would the Dexamethasone (Dex) suppression test be used? What are the expected effects in a healthy person versus someone with Cushing’s Disease?
Dex suppression test may be used in determining the cause of Cushing’s. Supplying Dex to a healthy person should reduce ACTH levels (because it is a Cortisol agonist). In someone with peripheral cortisol production (i.e. peripheral tumor), there is no change in ACTH.
Describe the pathophysiology and hormonal effects of a deficiency in 21-Alpha-hydroxylase enzyme.
Normally, 21-alpha is involved in production of Aldosterone and Cortisol hormones from Progesterone (P4). A deficiency in this enzyme results in a shunted pathway that produces HIGH levels of DHEA, 17-alpha-hydroxyprogestorone, A-Dione and Testosterone.
Thyroid disease is associated with what 2 signs/symptoms in women?
- Menstrual cycle irregularities
- Weight gain
- Abnormal levels of T3/4 and TSH