Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (935 page)

   Sideroblastic anemia

   Pregnancy

   Whipple disease

   Amyloidosis

   Limitations

   Serum folate is a relatively nonspecific test. Low serum folate levels may be seen in the absence of deficiency, and normal levels may be seen in patients with macrocytic anemia, dementia, neuropsychiatric disorders, and pregnancy disorders.

   Patients with low RBC folate or megaloblastic anemia should be evaluated for vitamin B
₁₂
deficiency. To distinguish between vitamin B
₁₂
and folate deficiency, determination of homocysteine (HCS) and methylmalonic acid (MMA) will help. In vitamin B
₁₂
deficiency, both HCS and MMA are elevated, whereas in folate deficiency, only HCS levels are elevated.

FOLLICULAR-STIMULATING HORMONE (FSH) AND LUTEINIZING HORMONE (LH), SERUM

   Definition

   These glycoproteins are produced by the anterior pituitary gland, regulated by hypothalamic gonadotropin-releasing hormone (GnRH) and feedback by gonadal steroid hormones. FSH stimulates follicular growth and stimulates seminiferous tubules and testicular growth. LH stimulates ovulation and production of estrogen and progesterone. LH controls production of testosterone by Leydig cells.

   
Normal range:
see Table 16.34.

TABLE 16–34. Normal Ranges of Human FSH and LH

   Use

   Diagnosis of gonadal, pituitary, hypothalamic disorders