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Biomedical subjects

D Igoe

Publications and source records attributed to D Igoe.

6 recordsLinked to original sources
PubMed1992

TSH as an index of L-thyroxine replacement and suppression therapy.

When hypothalamic-pituitary function is normal, serum TSH levels measured by ultrasensitive assay yield bioassays of endogenous thyroid action and thus provide an ideal index of thyroid secretion and its relationship to fluctuating endogenous thyroid levels. It is theoretically possible that patients receiving exogenous L-thyroxine for primary hypothyroidism should have suppressed TSH levels if physiological needs are constantly met. To examine this possibility free thyroxine, FT4 and TSH were measured in 90 clinically euthyroid patients receiving treatment with L-thyroxine for primary hypothyroidism. TSH levels were normal in 44, suppressed in 16 and elevated in 30 patients. FT4 levels were normal in 68, elevated in 13 and suppressed in 9 patients. Normal TSH levels were associated with normal FT4 levels in 79.5% of patients, elevated FT4 levels in 13.6% and low FT4 in 6.8%. Suppressed TSH levels were associated with elevated FT4 levels in 37.5% of patients and normal FT4 levels in 62.5%. When FT4 levels were normal, however, TSH levels were normal in only 51.5% and abnormal in 48.5%. We also examined the possibility that FT4 levels may remain within normal range when TSH is suppressed during L-thyroxine treatment for goitre or cancer. FT4 and TSH were measured in 45 patients on L-thyroxine as TSH suppression treatment. TSH was suppressed in 23 patients (51.1%), normal in 20 (44.4%) and elevated in 2 (4.5%). When TSH was suppressed, FT4 was elevated in 30.4% but normal in 69.6% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Nelson's syndrome following partial pituitary microadenomectomy and pregnancy.

We report for the first time the development of Nelson's syndrome in a patient who had previously undergone unsuccessful pituitary microadenomectomy and subsequently bilateral adrenalectomy. The removal of a 3-mm portion of a microadenoma did not protect against the development of Nelson's syndrome within 3 years which was closely related to pregnancy, a previously noted association. This report suggests that the development of Nelson's syndrome depends not on the size of the initial pituitary tumour but rather on its individual potential for proliferating once free of the inhibitory effects of glucocorticoid excess.

Adenoma, Chromophobe↗
PubMed1991

Sex steroids, adiposity and smoking in the pathogenesis of idiopathic hirsutism and polycystic ovary syndrome.

Hyperestronemia may be central to the development of polycystic ovary syndrome. The present study was designed to examine whether increased availability of androstenedione or increased aromatase closely associated with adiposity, plays the dominant role in the development of hyperestronemia. We measured plasma androstenedione, estrone and the estrone/androstenedione ratio (an indirect index of peripheral aromatase activity), in 141 patients with idiopathic hirsutism and in 88 patients with polycystic ovary syndrome. Estrone levels were higher in polycystic ovary syndrome, 250.4 +/- 129 (mean +/- standard deviation) than in idiopathic hirsutism, 210.6 +/- 119 pmol/l, p less than 0.05. Plasma androstenedione levels were higher in polycystic ovary syndrome, 8.24 +/- 3.5, than in idiopathic hirsutism, 7.1 +/- 1.7 nmol/l, p less than 0.0025. However, the estrone/androstenedione ratio was similar in the two groups. In all patients who smoked, androstenedione was higher, 8.14 +/- 3.22 than in nonsmokers, 6.99 +/- 2.96 nmol/l, p less than 0.005. Smokers had a lower body mass index, 23.9 +/- 2.3, than non-smokers 25.6 +/- 4.8 kg/m2, p less than 0.025. However, estrone levels were similar in smokers and in non-smokers. These data indicate that elevated estrone is more closely related to increased availability of androstenedione than to increased aromatase activity. While cigarette smoking appears to increase androstenedione levels, it may inhibit aromatase activity either directly or indirectly because of an associated reduction in adiposity. However, since the relative frequency of polycystic ovary syndrome and idiopathic hirsutism was similar in smokers and non-smokers, smoking did not appear to reduce estrone bioactivity as had been claimed.

Adrenal Glands↗
PubMed1990

The overnight dexamethasone test is a worthwhile screening procedure.

The overnight low-dose dexamethasone test is a convenient screening procedure for Cushing's syndrome. Claims that the test is associated with a high incidence of 'false positives', rendering it of little value particularly in obese and hospital in-patients, have been investigated in the present study. The data from 100 consecutive subjects undergoing overnight low-dose dexamethasone tests to examine for the possibility of Cushing's syndrome, were reviewed. Cushing's syndrome was identified in four patients, normal suppression of cortisol values occurred in 84 patients and 12 patients exhibited false positive results. Differences in body weights, body mass indices or in-patient status did not distinguish between those subjects with normal suppression of plasma cortisol and those subjects who yielded false positive results. These data indicate that the simple overnight dexamethasone test substituted for the more cumbersome traditional 48-h dexamethasone test in 84 of 96 patients who did not have Cushing's syndrome. Thus the overnight test provides a useful screening procedure but a small percentage of patients, approximately 12.5%, will require additional procedures to exclude Cushing's syndrome.

Adolescent↗