Advances in endocrinology and metabolism最新文献

Brittle diabetes is an uncommon complication of type I diabetes. However, the seriousness of the complication and its demands on the health care system warrant aggressive intervention. Studies during the last decade demonstrate that brittle diabetes is always secondary to a specific, identifiable etiology. This etiology is rarely apparent, however, without both extensive metabolic and psychological testing. In the long term, this testing is cost-effective inasmuch as approximately 50% of brittle diabetic patients are amenable to specific therapy. Several important issues have been clarified during the last decade, during which time major attempts have been made to understand the etiology of brittle diabetes. These issues may be summarized as follows: 1. There is always a specific etiology causing the brittle diabetes. 2. There are many different causes of brittle diabetes, but the most common are psychological abnormalities. 3. Therapy should always be directed at correcting the underlying pathogenic factor(s). 4. Empirical therapy and invasive procedures are contraindicated in brittle diabetic patients. 5. Extensive evaluation of a brittle diabetic patient may require referral of the patient to a diabetes center that has the expertise and manpower to appropriately evaluate a brittle diabetic patient. 6. Close follow-up and continued evaluation of therapy are necessary to confirm the suspected etiology and prevent diabetic ketoacidosis from developing. Unfortunately, only 50% of brittle diabetic patients respond to specific etiologic treatment. Research efforts during the next decade will focus on several clinical problems. First, improved psychological interventions are needed for common causes such as manipulative behavior and factitious disease. Second, treatment of severe systemic insulin resistance is still a major therapeutic challenge. Third, impaired glucose counterregulation needs to be better understood so that treatment is possible. The ultimate goal for physicians caring for brittle diabetic patients is to have effective therapy for all causes of brittle diabetes.

Calcium oxalate nephrolithiasis is a common syndrome that recurs and may be complicated by infection, obstruction, bleeding, and rarely, impairment in renal function. The formation of Ca oxalate stones depends on the state of urinary supersaturation with respect to Ca and oxalate and the action of urinary inhibitors of crystal nucleation, aggregation, and growth. Idiopathic hypercalciuria is the most common cause of Ca oxalate stones and is characterized by hypercalciuria, normocalcemia, and intestinal Ca hyperabsorption with or without elevated serum 1,25(OH)2D3 levels in the absence of other known causes of hypercalciuria. Current diagnostic evaluation of recurrent Ca oxalate nephrolithiasis should be conducted while the patients follow their usual diets and includes the following: 1. Analysis of stone composition by polarization microscopy. 2. Measurement of serum Ca, phosphate, uric acid, 1,25(OH)2D3, and creatinine. 3. Twenty-four-hour urine collection for an analysis of volume, pH, and excretion of Ca, phosphorus, magnesium, uric acid, citrate, sodium, oxalate, and creatinine. Therapy to prevent stone recurrence is designed to reduce urinary supersaturation of Ca oxalate by increasing urine volume, reducing urine Ca to below 200 mg/24 hr with thiazide, maintaining dietary Ca intake at 600 to 800 mg/day, and adding potassium citrate if urine citrate levels are reduced. If elevated, urine oxalate excretion can be reduced by dietary oxalate restriction. Stones less than 2 cm in diameter located in the renal parenchyma or upper urinary tract can be fragmented with ESWL, whereas larger stones or those in the lower urinary tract should be removed by either percutaneous nephrolithotomy or ureteroscopic procedures.

Patients with ambiguous genitalia stand a far better chance of receiving a rapid diagnosis, appropriate replacement therapy, and functional surgical reconstruction than was the case even a decade ago. Although the etiologies of true hermaphroditism and mixed gonadal dysgenesis remain elusive, most gene defects in female pseudohermaphroditism or CAH have been pinpointed to the 21-hydroxylase gene. Incomplete masculinization has been found to be due to defects in the androgen receptor, 5 alpha-reductase, or enzymes in the pathway from cholesterol to testosterone. SRY point mutations have been implicated in 46XY pure gonadal dysgenesis. Retained müllerian ducts have been attributed to point mutations in the MIS gene; those with normal MIS levels should be expected to have receptor deficits. In utero diagnoses and treatment and diagnosis at the preimplantation stage may prove to be very important for the care of some of these patients, who may be potential candidates for gene replacement therapy. When necessary, surgical reconstruction can be done. If the child is to be raised as a female, clitoral recession, labioscrotal reductions and advancements, and vaginoplasties for exteriorization can be accomplished in early infancy as an extensive one-stage procedure. If patients are to be raised as males, then various types of hypospadias repair can be done, gonads can be replaced with prostheses, the prepenile scrotum can be reconstructed, and müllerian structures can be removed with the goal of preserving the vas deferens. Replacement therapy with glucocorticoids and mineralocorticoids must be precisely managed to permit proper growth, and testosterone, estrogen, and progesterone replacement must be carefully considered and managed. A most important element in the care of these patients is the psychological support that first the families and then the patient require. This must be delivered with sensitivity. The proper care of these complex patients requires that the physician be a scientist as well as a clinician and a skilled technician.

The past decade has seen tremendous advances in both the diagnosis and treatment options for children with precocious puberty. Although the precise cause of CPP is still not known, long-acting GnRH analogues provide a safe and effective form of therapy. Treatment slows the progression of secondary sexual characteristics and rates of linear growth and bone maturation. Although the final verdict on how beneficial GnRH analogue therapy is in preserving the final adult height in children with precocious puberty is still not in, achieved heights are generally greater than pretreatment predicted heights. However, treatment may not be appropriate for all children with GDPP. Some children progress through puberty slowly and may not have significant compromise in final height. Furthermore, some children who come from tall families who may be subject to the same deterioration from target height as children who come from short families may not require therapy because their expected final heights may still fall within an acceptable range even if they are shorter than their siblings. Therapy offers the greatest advantage for those children in whom the onset of puberty is at a very early age, those who demonstrate rapidly accelerating bone age, or those with lower genetic height potential. In the past 3 years, the molecular mechanisms by which precocious puberty develops in children with MAS and FMPP have been elucidated. The molecular defects characterized explain the clinical manifestations. Future challenges will include the development of an effective, targeted form of therapy for gonadotropin-independent forms of precocious puberty.

Bisphosphonates are analogues of inorganic pyrophosphate, a naturally occurring chemical in bone. In vitro and animal experiments demonstrated that these agents were effective inhibitors of bone resorption. Subsequently they were applied to a variety of clinical problems in which increased bone resorption was an underlying feature of the pathology. In 1971 etidronate became the first bisphosphonate shown to inhibit bone resorption in humans when it was given to patients with Paget's disease. Subsequently this agent was also found to be useful in treating the hypercalcemia of malignancy. At the present time cyclic etidronate therapy is also used for the prevention of bone loss in patients with osteoporosis and for the prevention of heterotopic ossification in spinal cord-injured patients and in patients after hip replacement. Newer bisphosphonates are generally more potent than etidronate and do not produce a severe mineralization defect as do higher doses of etidronate. Pamidronate and clodronate are highly effective in the management of Paget's disease, hypercalcemia due to malignancy and immobilization, metastatic bone disease, and hematologic malignancies affecting bone. They are also promising agents for the prevention of osteoporosis. Alendronate, risedronate, and CGP 42446 are highly potent bisphosphonates that look very promising for the treatment of all disorders of bone resorption. It is fortunate that adverse reactions are not a prominent feature of bisphosphonate use. The main side effects are nausea and abdominal discomfort, mainly with oral use, a transient increase in bone pain in patients with Paget's disease, and an acute-phase reaction (fever, myalgia, mild leukopenia) in patients receiving aminobisphosphonates. The evolution of bisphosphonate therapy should be considered one of the major therapeutic events of the past 25 years. Future research should define the optimum use of these agents.