E. Nieschlag and H. Cüppers
E. Nieschlag and H. Bieniek
The endocrine testicular function in mink (Mustela vison) was investigated during the first year of life encompassing puberty, the first mating season and the phase of regression thereafter. The mink, relatively easily accessible as a semi-domesticated animal, was chosen as an example of a mammalian seasonal breeder. In plasma samples from 7 to 17 animals collected on 10 occasions between July and April testosterone and Δ4-androstenedione were determined by simultaneous radioimmunoassay. A steady increase of both androgens from November to early March, when the mating season occurs, and a rapid decline to pre-pubertal levels thereafter was observed. The ratio of testosterone to Δ4-androstenedione was 1:1 from November to April. These findings parallel the known morphological transitions of the testes.
Th. Schürmeyer and E. Nieschlag
Abstract. A single oral dose of 400 mg ketoconazole, a broad-spectrum antifungal drug, administered orally to 5 young men induced a drop in serum and saliva testosterone into the range of hypogonadism, while LH, FSH and prolactin levels remained unchanged. In vitro studies with mouse Leydig cells demonstrated a direct reversible inhibition of testosterone biosynthesis by ketoconazole. Comparative studies with chemically related compounds showed similar effects on testosterone production of mouse Leydig cells by isoconazole, miconazole, econazole and clotrimazole, while metronidazole and levamisole were without influence on testosterone biosynthesis. Since all tested imidazoles which suppress testosterone production have as a common feature a phenylated side chain of the imidazole molecule, this indicates a structure/activity relationship for the effects observed.
M Zitzmann and E Nieschlag
This review summarises the correlations between testosterone levels and male physical appearance and behaviour. Methodological shortcomings concerning the measurement of testosterone could limit the value of these findings. In addition, testosterone measured in body fluids represents only one step in the cascade of action from production to biological effect, and could therefore provide only a limited view of the complexity of physiological events. Testosterone levels are influenced by conditions that are partly controlled or initiated by the hormone itself, but also by circumstances beyond hormonal or individual control. Different kinds of behaviour are not only subject to influence by environment, but also androgens can reinforce the particular kind of conduct and the behavioural impact can wield negative or positive feedback on testosterone secretion. Therefore, both generalisation and individualisation of study results will lead to doubtful conclusions and prejudices. Results of such studies must be viewed with caution, and over-simplification as well as over-interpretation should be avoided.
E. Jean Wickings and E. Nieschlag
Adult male rhesus monkeys are aggressive animals and very difficult to handle. Hence experimental manipulations necessarily involve the use of restraint procedures, either chemical or physical, which may influence endocrine functions. Therefore, the effects of ketamine anaesthesia on basal hormone levels and on the pituitary response to LRH and TRH were investigated in 4 adult male rhesus monkeys. Values were compared to those obtained from the same animals restrained in primate chairs for approximately 48 h, a procedure to which they had been accustomed to over the preceding 6 months.
Serum cortisol levels under anaesthesia were at all times lower than in conscious monkeys, but increased after 2 h to values twice as high as measured initially. Serum testosterone concentrations were not significantly different on the two occasions, but levels under anaesthesia were slightly higher initially than in the conscious monkeys, and decreased gradually over the 3 h test period. Initial prolactin levels were lower in the anaesthetized monkeys, and increased 2–3-fold after 90 min; values at 3 h were not significantly different from those in conscious monkeys. Intravenous TRH elicited a similar response in prolactin on both occasions, maximum values occurring after 15–30 min and returning to basal levels after 3 h. The maximum values attained and the area under the response curves were higher under anaesthesia. LRH stimulation resulted in a 15- and 30-fold increase in serum levels of biologically active LH, with and without anaesthesia, respectively. Basal levels were not significantly different on the two occasions. The area under the LH response curve was higher in 3 of the 4 monkeys without anaesthesia.
The extent to which results in conscious monkeys are affected by stress is difficult to assess. Since neither handling technique allows for the collection of 'true' basal data, it is paramount to standardize and define the conditions under which experiments, and even routine blood sampling, are performed in male rhesus monkeys.
E. J. Wickings and E. Nieschlag
In order to evaluate the endocrine testicular and adrenal function of rhesus monkeys in vivo, and to compare this with the human situation, the effect of dexamethasone (Dxm), HCG and combined Dxm/HCG administration on the steroid levels was investigated in 8 adult male rhesus monkeys in November/December (= season of high testicular activity). Serum levels of cortisol, testosterone (T), androstenedione (A), 17-hydroxyprogesterone (17-OHP), oestradiol (Oe2), dehydroepiandrosterone (DHA) and its sulphate (DHA-S) were measured radioimmunologically.
Basal T and DHA serum levels were similar to those found in man, whilst A levels amounted to 1/10 and DHA-S to 1/30 of human values. Oe2 and 17-OHP levels were higher than in man. T and A levels were not suppressed by Dxm and very high degrees of stimulation were reached after HCG. The HCG-induced increment in T was smaller under Dxm/HCG than under HCG alone. 17-OHP levels were reduced to 25% of basal levels under Dxm, but the incremental response to Dxm/HCG was the same as that without Dxm. DHA and DHA-S were 60 and 75% lower under Dxm, and the increment in DHA after Dxm/HCG was less than that after HCG. DHA-S did not respond to HCG.
In conclusion, several important differences in basal steroid levels and in the response to dynamic testing were found in the rhesus monkey, as compared to man. The adrenal contributes 75% to circulating 17-OHP levels, and 60 and 75% respectively to DHA and DHA-S levels. A is produced solely by the testis in the rhesus monkey. As compared to man, the rhesus monkey testis in vivo synthesises T via both the Δ4 and Δ5 pathways. The Δ5 pathway appears to be dependent on adrenal steroid precursors.
E. Nieschlag and H. K. Kley
Ch. Witting, E. J. Wickings and E. Nieschlag
Before immunisation with hormones can be applied in therapeutic medicine, the possible immunological side effects should be investigated. Therefore the kidneys of 20 rabbits immunised with testosterone-BSA conjugates were examined 4 to 30 weeks after immunisation for the presence of immune complex precipitation and glomerulonephritis. Eighty-five per cent showed differing degrees of precipitation and 50 % had an exudative glomerulonephritis. None of the kidneys from normal control rabbits or those immunised with complete Freund's adjuvant or BSA showed any signs of immune complex precipitation, although high anti-BSA titres were present in the BSA-immunised animals (1/3000 – 1/25 000). BSA antibodies could not be detected in the rabbits immunised with testosterone-3-BSA. In the light of these findings active immunisation with steroid-BSA conjugates would not be advisable as a means of therapy.
E. Nieschlag, E. J. Wickings and J. Mauss
In order to detect any possible Leydig cell dysfunction associated with male infertility, the endocrine capacity of the testes was investigated in vivo and in vitro in 21 infertile men. Plasma testosterone was determined before and after 3 days of hCG stimulation. Testicular tissue obtained by bilateral biopsies was subjected to (1) histological examination, (2) determination of basal testosterone concentration and (3) incubation with hCG. Patients were grouped according to histology. In vitro basal and stimulated testicular testosterone was similar in patients with normal histology, Sertoli-cell-only syndrome and spermatogenic arrest. Tissue from patients with Leydig cell hyperplasia showed 3-fold higher basal testosterone levels and a greater response to hCG. All patients had plasma testosterone levels and responses to hCG in the normal range. There was no significant correlation between the data obtained in vivo and in vitro, indicating that testosterone determinations in peripheral blood do not necessarily reflect the intratesticular situation. There was no evidence for gross abnormality in Leydig cell function accompanying disturbed spermatogenesis.