Clinical Chemistry VI Flashcards
Endocrinology
Consists of several glands that secrete hormones directly into the blood rather than into a duct system
Amines
Single amino acids
-T3, T4
Peptide and protein
Pituitary gland hormones
Steroid
Converted from cholesterol
-Glucocorticoids, estrogens
Professor Nowak’s Endocrinology Rule
95% of endocrinology disorders are due to primary gland dysfunction
Glands in endocrinology
Hypothalamus Pituitary Thyroid Adrenals Parathyroid Pancreas
Hypothalamus
Synthesizes hormones
Stimulate or inhibit the secretion of pituitary hormones
Controls body temp, hunger, attachment behaviors, thirst, fatigue, sleep, and circadian rhythms
Anterior pituitary hormones
Growth hormone (GH) Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Prolactin (PRL) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Melanocyte-stimulating hormone (MSH)
Posterior pituitary hormones
Oxytocin- uterine contractions, lactation
Vasopressin (antidiuretic hormone, ADH)
Kidney water reabsorption and excretion
Acromegaly and giantism
Too much growth hormone (GH) usually from pituitary adenoma
Sx of acromegaly and giantism
Overgrowth of skeleton and soft tissues
Lab of acromegaly and giantism
Increased growth hormone
Increased serum insulin-like growth factors (IgF-1)
-IgF-1 circulates in much higher plasma concentrations than GH and is a good screening test of suspected GH abnormalities and for monitoring therapy in pts
-Single measurements of GH are not often reliable because GH secretion is episodic and diurnal
Hyperprolactinemia
Too much prolactin usually due to pituitary adenoma (pregnancy, chronic renal failure, medications)
Sx of hyperprolactinemia
Infertility Anovulation Menstrual irregularity Amenorrhea Oligospermia Impotence Gynecomastia
Labs of hyperprolactinemia
Elevated prolactin level
Tx for hyperprolactinemia
Dopamine agonists (cabergoline, bromocriptine)
Central diabetes insipidus
Deficiency of ADH (diuretic effect)
Sx of central diabetes insipidus
Dehydration (urinates up to 20L per day)
Normal-high serum sodium and osmolality
Low urine sodium and osmolality
Labs for central diabetes insipidus
Hypernatremia
Decreased ADH
Tx for central diabetes insipidus
Desmopressin
Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
Too much ADH (tumors that secrete ADH)
-MDMA, sarcoidosis, pulmonary disease, medications
Sx of SIADH
Muscle weakness Ataxia Tremor Lethargy Confusion Delirium Seizures
Thyroid gland
Produce hormones that affect body metabolism
- Triiodothyronine (T3)
- Thyroxine (T4)
- Calcitonin
Triiodothyronine (T3)
Minority, but more active hormone
Thyroxine (T4)
Majority, prohormone
Both T3 and T4 contain iodine and are transported to tissues by plasma proteins
Thyroxine-binding globulin (TBG)- 70%
Transthyretin (10-15%) and albumin (15-20%)
Calcitonin
Related to calcium homeostasis
Also a tumor marker for medullary thyroid carcinoma
Thyroid stimulating hormone (TSH) lab test
Pituitary hormone that stimulates the thyroid gland to produce T4 and then T3 Nl range: 0.3-3.0 Increased: Primary hypothyroidism -Secondary hyperthyroidism Decreased: Primary hyperthyroidism -Secondary hypothyroidism
Total T3 and/or T4
Measures amt that is bound to thyroxine-binding globulin (TBG)
Less useful with protein abnormalities
Free T3 (0.3%) or T4 (0.03%)
May need to be ordered after TSH reviewed
More expensive test compared to TSH
Antithyroid antibodies
Antimicrosomal/antithyroid peroxidase antibodies (anti-TPO)
Antithyroglobulin antibodies
TSH receptor antibodies
Antimicrosomal/antithyroid peroxidase antibodies (anti-TPO)
Directed against the protein enzyme TPO
Seen in Hashimoto thyroiditis (99%) and Graves disease (85%)
Antithyroglobulin antibodies
Hashimoto thyroiditis (85%) and Graves disease (30%)
TSH receptor antibodies
Immunoglobulins that bind to TSH receptors and influence their action (usually stimulate thyroid like in Graves disease)
Radioactive iodine uptake and thyroid scan
Nuclear imaging scan of administered radioactive iodine
Low uptake suggests thyroiditis
High uptake suggests Graves disease
Unevenness in uptake suggests the presence of a nodule
Thyroglobulin
Stored in the follicular colloid of the thyroid as a prohormone
Used to monitor tx in thyroid cancer
Hyperthyroidism (thyrotoxicosis)
Too much T3/T4 is being made
- Primary- thyroid gland makes too much T3/T4
- -Pituitary then decreases the amt of TSH
- -95% of all hyperthyroidism
- Secondary- pituitary makes too much TSH
- -Acts on the nl thyroid to make too much T3/T4
- Tertiary- hypothalamus makes too much TRH
- -Acts on the nl pituitary to then make too much TSH
Sx of hyperthyroidism
Hypermetabolic features Nervousness Palpitations Muscle weakness Increased appetite Diarrhea Heat intolerance Warm skin Weight loss Perspiration Exopthalmous Emotional changes Menstrual changes Fine tremor
Graves disease
Autoimmubne disease caused by TSH receptor antibodies that bind to and stimulate TSH receptors resulting in autonomous production of thyroid hormone
Labs: Graves disease
High T3/T4
Low TSH
Diffuse radioactive iodine uptake
+ TSH receptor antibodies
Tx for Graves disease
Radioiodine therapy
Medications
Thyroid surgery
Subacute thyroiditis
Secondary to viral infection, lasts for months
Labs: subacute thyroiditis
High T3/T4
Low TSH
High ESR
No radioactive uptake
