Christina Yan Wang

CHANGES IN THE PITUITARY-TESTICULAR SYSTEM WITH AGE

In order to provide a comprehensive account of pituitary‐testicular function in man, 466 subjects, ranging in age from 2 to 101 years, were studied to examine blood levels of the pituitary gonadotrophins (LH and FSH), the sex steroids testosterone and oestradiol, the binding capacity of the sex hormone binding globulin (SHBG), the free testosterone and oestradiol fractions, and the transfer constant for the peripheral conversion of testosterone to oestradiol. The results were compared with clinical indices of testicular size, sexual function and secondary sex hair distribution. Serum LH and FSH were low before puberty, increased in pubertal adolescents to levels somewhat above those of adults and subsequently increased progressively over the age of 40 years. Testosterone levels fell slowly after the age of 40, while there was a slight rise in plasma oestradiol with increasing age. FSH and testosterone showed small seasonal variations in young adult men, the lowest values being seen in winter. SHBG binding capacity was high in two prepubertal boys, fell in adult men, but increased in old age. Free testosterone and oestradiol levels fell in old age. The metabolic clearance rates (MCR) of testosterone and oestradiol also fell in old age, while the conversion of testosterone to oestradiol was increased. Many correlations were observed between various hormonal and clinical measurements. The evidence is consistent with a primary decrease in testicular function over the age of 40 years.

Comparison of the effectiveness of placebo, clomiphene citrate, mesterolone, pentoxifylline, and testosterone rebound therapy for the treatment of idiopathic oligospermia

Forty-six subfertile men with idiopathic oligospermia were randomly assigned to 6 months of treatment with a placebo, clomiphene citrate (25 or 50 mg/day), mesterolone (100 mg/day), or pentoxifylline (1200 mg/day) or 4 months of testosterone enanthate treatment (100 or 250 mg on alternate weeks). Treatment with the placebo, mesterolone, pentoxifylline, and testosterone rebound therapy did not result in a significant increase in the mean sperm concentration or pregnancy in the partners. Clomiphene citrate at both dosages significantly increased the mean sperm concentration without improving sperm motility or morphology during the 6-month treatment period. Pregnancy rates of 36.4% and 22.2% were observed in partners of men receiving clomiphene citrate 25 mg/day and 50 mg/day, respectively. This study also illustrates the difficulties in identifying suitable patients for and assessing the efficacy of different treatment regimens.

HORMONAL STUDIES IN KLINEFELTER'S SYNDROME

Some aspects of the hormonal abnormalities of Klinefelters syndrome have been studied in nineteen patients. As a group the plasma production rate, the total and free levels of testosterone, and the metabolic clearance rates of testosterone and oestradiol were low. Plasma oestradiol, LH and FSH levels were elevated and there was increased peripheral conversion of testosterone to oestradiol. The production rates of oestradiol and the binding capacities of the sex steroid binding globulin were normal. There were fluctuations in the blood levels of LH, FSH, testosterone and oestradiol, but these appeared to be less marked than in healthy men. Both LH and FSH levels were suppressed by acute or prolonged testosterone administration and there was no evidence for a differential effect on LH. It is suggested that the threshold for suppression of LH and FSH is increased in hyper‐gonadotrophic states. Although no statistically significant relationships were found between the hormonal and clinical abnormalities of the syndrome it is probable that the hyperoestrogenism and androgen deficiency are linked to the development of the signs of feminization and hypogonadism.

Determination of low concentrations of platinum group elements in geological samples by ID-ICP-MS

Accurate and precise determination of platinum group elements (PGEs) at ppb concentrations in geological samples is important but problematic. This paper reports an improved analytical method for the determination of Pt, Pd, Ru, Ir and Rh at sub-ppb levels by isotope dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS). Prior to experimentation, all reagents were carfully purified: HBO3, HCl and SnCl2 by Te coprecipitation and HNO3 and HF by subboiling distillation. HF, HNO3 and HCl were used to decompose 10 gram sample. The fluoride residue from the acid digestion is minimized by using H3BO3 for complexation, thus mini-fusion of sodium peroxide can be performed in corundum crucibles instead of bulk Na2O2 fusion to lower blank level. The solution of acid digestion and Na2O2 fusion are combined and PGEs are then pre-concentrated by Te coprecipitation. Cu, Ni, Zr and Hf are removed using cation exchange resin and P507 extraction chromatography resin combined in the same column to minimize their interference. Pt, Pd, Ru and Ir are determined using ID-ICP-MS, whereas the mono-isotopic element, Rh, is determined by external calibration using highly enriched 194Pt as the internal standard. The enriched 194Pt spike behaves similar to Rh during the Te precipitation procedure and acts as an ideal internal standard. The determination limits for PGE range from 0.01–0.19 ng g−1. The results obtained using this new method for the CCRMP (CANMET, Ottawa, Canada) certified reference materials WGB-1 (gabbro), TDB-1 (diabase) and UMT-1 (ultramafic ore tailings), show good agreement with the reported values, but have discrepancies compared with the certified values when the concentration of Ru, Rh and Ir below 0.5 ng g−1.

Geochemistry of the Early Paleozoic Baiyin Volcanic Rocks (NW China): Implications for the Tectonic Evolution of the North Qilian Orogenic Belt

The Qilian Mountains in NW China comprise the North Qilian Orogenic Belt, Central Qilian Block, and South Qilian Orogenic Belt. The North Qilian Orogenic Belt consists of the Northern and Southern terranes separated by a volcanic rock belt. This belt is composed mainly of felsic and mafic volcanic rocks. Volcanic rocks in the Baiyin area of the eastern part of the belt include rhyolites, rhyodacite, andesitic basalts, and basalts. New zircon U‐Pb isotopic data yield a crystallization age of ca. 445 Ma for the rhyolite, 30 m.yr. younger than the associated basalts. The mafic volcanic rocks are relatively enriched in Th, Sr, and light rare earth element with (La/Yb)N ratios ranging from 4.2 to 5.6 and LaN ranging from 40 to 49, and depleted in high field strength elements, with high Th/Nb ratios (0.9–1.3). These features together with their ϵNd(T) values (−1.4 to +3.1) are consistent with a subduction‐related origin, most likely in a mature island arc or an arc built on thin continental crust in an active continental margin. The felsic volcanic rocks show a calc‐alkaline affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies and relatively high Th/Nb ratios (0.8–1.6). They have significantly high ϵNd(T) values (+4.4 to +7.7) relative to the mafic volcanic rocks. Such radiogenic Nd isotopic compositions rule out a crustal origin and indicate the derivation from a depleted mantle source in a volcanic arc environment. Therefore, the geochemistry of the mafic and felsic volcanic rocks demonstrates an Ordovician volcanic arc above a northward subduction zone. The northward drifting of the Central Qilian Block eventually resulted in the amalgamation of the Northern and Southern terranes to form the North Qilian Orogenic Belt in the Early Paleozoic.

THE EFFECT OF HEROIN ADDICTION ON PITUITARY-TESTICULAR FUNCTION

The effect of heroin addiction on pituitary‐testicular function was studied in 54 active and 19 abstinent addicts and their results were compared with those of 43 age‐matched controls. Abnormal sexual function was frequently found in heroin addicts and this persisted after drug withdrawal. The mean total (mean ± SE, 18.1 ± 1.0 nmol/l) and free (0.17 ± 0.03 nmol/l) testosterone (T) levels in heroin addicts were significantly lower than those in healthy controls (total T 22.8 ± 1.1 nmol/l, P < 0.005; free T 0.30 ± 0.03 nmol/l, P < 0.005). The mean sex hormone binding globulin binding capacity was higher in heroin addicts (60.1 ± 5.2 nM) than in healthy controls (35.5 ± 2.1 nM). These hormonal changes returned promptly to normal after withdrawal. The basal LH and FSH and the responses to LHRH were comparable in the three groups studied.

Intrauterine insemination is not useful in oligoasthenospermia

Abstract A prospective randomized study was conducted in 4 7 couples with infertility due to subnormal semen to compare luteinizing hormone (LH)-timed intrauterine insemination with LH-timed natural intercourse. No pregnancy occurred in 114 cycles of intrauterine insemination with washed sperm. Only one patient conceived during 1 of the 124 natural intercourse cycles. The only complication that occurred after intrauterine insemination was mild abdominal cramp in 3 cycles. The authors conclude that intrauterine insemination is not useful in the management of subfertility due to oligoasthenospermia.

A practical method for determination of molybdenite Re-Os age by inductively coupled plasma-mass spectrometry combined with Carius tube-HNO3 digestion

A simplified method for the determination of molybdenite Re-Os ages using inductively coupled plasma-mass spectrometry (ICP-MS) is presented. By the means of Carius tube method, molybdenite and pyrite were digested using concentrated HNO3, and were then changed into MoO3 and Fe(NO3)3 precipitates, respectively. Rhenium was determined directly by ICP-MS after removal of Os by heating for the molybdenite supernatant or by cation-exchange purification for the pyrite supernatant. Osmium distilled as OsO4 from the supernatant was trapped using pure water and could be directly analyzed by ICP-MS. This method was validated using two molybdenite reference materials, GBW 04435 and GBW 04436, and their Re-Os ages obtained are 220.3 ± 1.1 Ma (1.0%, 2s), and 140.5 ± 0.9 Ma (1.2%, 2s), respectively, consistent with literature values. The proposed Re-Os dating method was applied to molybdenite and pyrite sampled from a porphyry Mo-deposit. The results show that this deposit is the oldest Mo-deposit so far found in China.

Addisonian crisis as presenting feature in malignancies

Metastases to the adrenal glands are common in patients with malignancy but malignant disease presenting as Addisonian crisis is rare. The authors presented two patients with acute Addisonian crises due to metastatic infiltration of the adrenal glands. They were otherwise asymptomatic from the primary tumor. Computed tomographic scan showed bilateral adrenal enlargement and transcutaneous biopsy confirmed metastatic adenocarcinoma in the adrenals. Adequate glucocorticoid replacement improves quality of life and prolongs survival.

Use of low-dosage oral cyproterone acetate as a male contraceptive☆

To ascertain the effects of low-dosage cyproterone acetate (CPA) on the reproductive and endocrine functions of normal men, 25 volunteers were given CPA 0, 5 or 10 mg daily over 16 weeks, preceded by 12 weeks pretreatment observation and followed by 24 weeks posttreatment follow-up. CPA caused a decrease in sperm concentration, percentage motility, proportion of normal sperm and ability of the sperm to penetrate a column of cervical mucus in most patients. In addition, circulating testosterone, estradiol, LH and FSH levels were significantly reduced during treatment. All these changes reverted to the pretreatment level upon drug withdrawal. These findings suggest that firstly, although low dosage CPA was able to induce changes in seminal analyses, azoospermia was present in only one out of 15 subjects exposed to the drug. Secondly, the marked decrease in androgen levels associated with CPA treatment renders CPA unsuitable as a single entity agent for long-term male contraception.