Endocrine Function II Part 2
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Describe lab results found in TSH-Dependent (secondary or tertiary) hyperthyroidism.
Increased T3/T4, increased TSH (thyroid normal but ant. pit. not working), decreased TRF (TRH-secondary) or increased TRF (TRH-tertiary)
Describe lab results found in TSH-Independent (Primary) Hyperthyroidism.
Increased T3/T4, Increased Free T4/T3, Decreased TSH (because the ant. pit. is normal), Decreased TBG, Increased THBR, and Decreased TRH (also called TRF); this occurs because negative feedback is turned off and the problem is occurring in the thyroid gland
What does the TRH stimulation test differentiate?
Normal response=Tertiary Hypothyroidism; Blunted Response=Secondary Hypothyroidism
State the use of Total T3 assays.
Measures both free and bound hormone; aids in diagnosis and monitoring of hyperthyroid patients with decreased TSH and normal Free T4
The clinical use of this test is to directly or indirectly assess available TBG binding sites but is not to diagnose hyper- or hypo- thyroidism. May be ordered if the patient has abnormal total T4 or total T3 levels with a normal TSH.
THBR- Thyroid Hormone Binding Ratio with T3 Uptake Test
The clinical use of the test is primarily to monitor patients with follicular thyroid cancer (which would be increased); it is the storage form of the thyroid hormone precursors
Thyrogobulin
This is the most sensitive and specific mesaure of thyroid activity
TSH
This test aids in diagnosis and monitoring of hyperthyroid patients with suppressed TSH levels and normal Free T4 levels
Total T3
This test by itself, does not provide enough clinical information and must be reported in conjunction with the other thyroid tests.
Total T4
This test provides an approximation of the free hormone concentration in the presence of abnormal TBG levels as TBG or free hormone levels are not easily measured
THBR
State the SPECIFIC diagnostic usefulness of the following -Antithyroidglobulin antibody (TgAb)
Hashimoto’s thyroiditis >85% reactivity, grave’s disease >30% reactivity, and also a tumor marker for recurrence of thyroid cancer
State the SPECIFIC diagnostic usefulness of the following -Thyroid peroxidase autoantibody (TPOAb)
-Hashimoto’s thyroiditis 100% reactivity, Grave’s disease 70-80% reactivity; Ab itself may be cytotoxic to the thyroid
State the SPECIFIC diagnostic usefulness of the following -TSH receptor autoantibody (TRAb)
Immunoglobulins that bind to thyroid cell membranes at or near TSH receptor site; hyperactivity in Grave’s or inability for TSH to stimulate the thyroid in Hashimoto’s; provides differential diagnosis of hyperthyroidism, predicts fetal dysfunction, and predicts course of grave’s patients on antithyroid drug therapy
What is the number of carbons present in estrane?
18
What is the number of carbons present on androstane?
19
What is the number of carbons present on pregnane?
21
What is the analytical importance of the phenolic hydroxyl group on carbon #3 on estrane and its derivatives?
Estrogens on carbon #3, androgens do not have this
What are the biological effects of estrogen?
primary and secondary sexual characteristics
What is the site of production of estrogen?
Graafian follicle of ovaries
What is the most potent, physiologically active estrogen?
Estradiol, evaluates ovarian function
What is the major post-menopausal estrogen?
Estrone
What is the major estrogen produced during pregnancy?
Estriol, decreased in fetal distress and measured to monitor progress of pregnancy
Describe the menstrual cycle with the rise and fall of estrogen, FSH, and LH
E2 removes negative feedback for FSH/LH which increases FSH and increases estrogen.
What is the SPECIFIC biological effect of FSH in women
Chooses an egg