Comparison between the plasma concentrations of prolactin and parathyroid hormone in normal subjects and in patients with hyperparathyroidism or hyperprolactinemia

Sexual Dysfunction in Women With Kidney Disease

Sexual health is inversely associated with estimated glomerular filtration rate and is associated with adverse cardiovascular outcomes, depression, poor self-image, and impaired quality of life. Many women with chronic kidney disease (CKD) and ESKD experience symptoms of sexual dysfunction which is underrecognized secondary to a variety of factors including physicians' discomfort in discussing sexual health, patients' reluctance to bring up sexual health, difficulty in the assessment of sexual health in comparison to men, and the overall lack of well-conducted clinical studies in women. The pathophysiology is not fully understood but likely involves changes in sex hormones throughout the hypothalamic-pituitary-ovarian axis. Proper evaluation of this axis is necessary as treatment is tailored to these findings and can improve outcomes. A comprehensive assessment of sexual dysfunction inclusive of women with varying gender identification and sexual orientation, partnered with recognition and treatment of contributing factors as well as identifying the underlying cause, is paramount. With the lack of studies, particularly in women with CKD, treatment options, in some cases, can be considered unchartered territory. In this article, we will review available evidence on the pathophysiology, clinical manifestations, and treatment for sexual dysfunction in women with CKD and ESKD.

Serum prolactin levels in a uremic child: effects of bilateral nephrectomy and kidney transplantation

Elevated levels of serum prolactin (PRL) are common and well described in patients with chronic renal failure. We report the case of a 4-year-old girl who also presented with premature thelarche and transient galactorrhea. Neither peritoneal dialysis nor hemodialysis reduced her extremely elevated levels of PRL, which fluctuated from time to time, probably reflecting variations in lactotroph secretion rate. Bilateral nephrectomy (BN) was eventually followed by a progressive and significant rise in PRL levels, suggesting that even uremic kidneys can eliminate PRL through tubular breakdown. Kidney transplantation was responsible for a very abrupt normalization of PRL serum levels, much faster than that observed for creatinine. This confirms animal studies suggesting that elimination of PRL occurs both through glomerular filtration and tubular breakdown. We hypothesized that the seemingly precocious puberty may have resulted from a combination of growth hormone therapy, elevated PRL and a rise in estrogens through the aromatization of adrenal androgens. This case illustrates the impact of dialysis, BN and kidney transplantation on PRL, providing new knowledge on renal PRL metabolism.

Parathyroid hormone, a uremic toxin

Despite the innovations in the treatment of secondary hyperparathyroidism, there are uremic patients with marked elevation in PTH levels. Uremic toxicity is in part attributable to the excess of circulating PTH. It has been known for many years that PTH may induce changes in cell calcium, a key intracellular signal required for normal cell function. The effect of PTH in dialysis patients is not limited to bone; the diversity of biologic effects of PTH is summarized in this review. In addition, the present review addresses other issues: (i) the presence of different circulating PTH fragments in uremic patients, (ii) the PTH assays currently utilized to measure circulating PTH, and (iii) the fact that some of the PTH effects seen in uremic patients may be due to the interaction of C-terminal PTH fragment with putative C-terminal PTH receptors.

[Primary hyperparathyroidism in special situations: multiple endocrine neoplasia syndromes and parathyroid cancer]

Primary hyperparathyroidism (PHP) is a known endocrine disorder. Many years ago, the most frequent forms of clinical presentation were symptomatic renal or skeletal disease with moderate or severe hypercalcemia; however, currently, most patients have few symptoms and mild hypercalcemia. The last NIH Workshop on Asymptomatic PHP developed criteria for the management of this disease. Multiple endocrine neoplasia (MEN) types 1 and 2 are two genetic syndromes caused by different types of molecular abnormalities. PHP is the most common manifestation of MEN-1 and is the last feature to appear in MEN 2A. Parathyroid carcinoma (PC) is a rare neoplasm and an uncommon cause of parathyroid hormone (PTH)-dependent hypercalcemia. In this report, the treatment of PHP in MEN syndrome and PC are reviewed. Special attention is paid to a new class of drugs called "calcimimetics", which are powerful compounds that may be highly useful in the treatment of both conditions.

Formulations for intermittent release of parathyroid hormone (1-34) and local enhancement of osteoblast activities

The objective of these studies was to develop simple, implantable devices that intermittently release PTH(1-34) and thus could be used for locally stimulating bone formation. The formulations were based on the association polymer system of cellulose acetate phthalate and Pluronic F-127. Release profiles for intermittent devices showed five discrete peaks, whereas sustained devices exhibited zero-order kinetics. Osteoblastic activity was greater for cells intermittently treated with PTH(1-34) compared to sustained exposure. These controlled release devices delivering PTH(1-34) in an intermittent manner may be useful for affecting osteoblast activities in a localized area.

Serum Parathyroid Hormone Concentrations Are Increased in Women with Polycystic Ovary Syndrome

Background: The present study was designed to investigate the effects of polycystic ovary syndrome (PCOS) and of obesity on serum parathyroid hormone (ΡΤΗ), 25-hydroxyvitamin D (25-OH-vitamin D), and 1,25-dihydroxyvitamin D [1,25-(OH)2-vitamin D] concentrations and the possible associations of the above calciotropic hormones with the hormonal and metabolic characteristics of the syndrome.

Methods: We studied 58 obese [body mass index (BMI) >30 kg/m2] women with PCOS, 64 overweight (ΒΜI, 25–30 kg/m2) women with the syndrome, 169 normal-weight (BMI <25 kg/m2) women with PCOS, 29 obese controls (ovulatory women without clinical or biochemical hyperandrogenemia), 14 overweight controls, and 70 normal-weight controls. Blood samples were collected (at 0900 after an overnight fast) between the 3rd and 6th days of a menstrual cycle in the control groups and during a spontaneous bleeding episode in the PCOS groups. Circulating concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), testosterone, Δ4-androstenedione, 17α-hydroxyprogesterone, sex-hormone–binding globulin (SHBG), insulin, glucose, PTH, 25-OH-vitamin D, and 1,25-(OH)2-vitamin D were measured.

Results: Both PCOS and increased body weight had a significant positive effect on serum PTH values. PTH concentrations were significantly correlated with age, BMI, glucose, PRL, SHBG, and testosterone. Only the correlations with testosterone and PRL were BMI-independent. The effect of PCOS on PTH concentrations remained significant after adjustment for BMI, but not after adjustment for testosterone concentration. Increased body weight also had a significant negative effect on 25-OH- and 1,25-(OH)2-vitamin D concentrations, but no association with the syndrome was observed.

Conclusions: The results of the present study are in agreement with previous data supporting an association of increased PTH and decreased vitamin D metabolite concentrations with obesity. Moreover, the present findings indicate, for the first time, that PTH probably is also linked to PCOS-associated hyperandrogenism.

Malignant Thymic Carcinoid in Multiple Endocrine Neoplasia Type I Syndrome: Case Report and Literature Review

OBJECTIVE

To describe a case of thymic carcinoid tumor in association with multiple endocrine neoplasia type I (MEN I) and discuss the various manifestations of this syndrome.

METHODS

We present the clinical and laboratory data, including histopathologic and immunocytochemical findings, for our current patient and also review the literature on MEN I syndromes.

RESULTS

In a 46-year-old Caucasian man with no family history of multiple endocrine neoplasia, numerous MEN I lesions developed over time. The patient had gastrinoma of the duodenum, Zollinger-Ellison syndrome, hyperparathyroidism, a nonfunctioning adrenal mass, and foregut carcinoid tumors, including gastric and malignant thymic carcinoids. He sequentially underwent partial gastrectomy in conjunction with Billroth II anastomosis, a four-gland parathyroidectomy, and palliative radiotherapy for malignant carcinoid tumor, as well as endoscopic excision of accessible tumors.

CONCLUSION

The involvement in MEN I can be clinically complex. Early detection of MEN I lesions will facilitate timely implementation of treatment and help minimize complications.

Effects of excess PTH on nonclassical target organs

The classical target organs for parathyroid hormone (PTH) are the bone and kidneys. In uremia, however, numerous studies have shown that PTH may also affect the function of a number of nonclassical organs and tissues besides the bone and kidney, including the brain, heart, smooth muscles, lungs, erythrocytes, lymphocytes, pancreas, adrenal glands, and testes. Most of these effects do not apply to the generally accepted actions or normal regulatory mechanisms of PTH. Thus, the potential role of PTH as one of the possibly many toxins in uremia is of current interest. The molecular basis for the actions of elevated PTH levels on various nonrenal and nonskeletal organs or tissues might be mediated via the widespread distribution of the classical PTH/PTH-related peptide (PTHrP) receptors and via the novel PTH2 receptors. The present survey deals with an evaluation of the nonrenal and nonskeletal effects of excess PTH in uremia, taking into consideration the presently available information on the organ-specific expression of the classical and novel PTH receptors, and of the expression and function of PTHrP.

Controversies in surgical therapy for APUDomas

Location of gastrinomas by means of portal venous sampling is a technique in which venous blood from various sites in the portal system around the pancreas and duodenum is obtained and assayed for gastrin levels. A gradient of 50% or greater compared to systemic gastrin levels from a given location regionally identifies the site of gastrin overproduction, thereby locating the tumor. The only area in which venous sampling may help, in the authors' opinion, is in the small subset of patients who have occult gastrinoma not imaged with any other modality, in the body or tail of the pancreas that cannot be found with intraoperative ultrasound or palpation. It is considered that a secretin angiogram is equally effective and is a simpler procedure. Similarly, in insulinoma regional location of the tumor by means of a calcium angiogram has eliminated the usefulness of portal venous sampling. Controversial areas of surgical treatment of APUDomas often reflect a balance between the risks and benefits of aggressive surgery, as data to support an aggressive surgical approach to obtain improved survival often do not exist. For example, if patients with occult MTC can undergo cervical reexploration with minimal or no morbidity the potential benefit of removing malignant disease, warrants this approach. Similarly, if patients with MEN-1 can be explored safely with resection of pancreatic and duodenal tumors, then this position can be defended. On the other hand, if a subgroup of patients with MEN-2 and pheochromocytomas can be spared bilateral adrenalectomy without compromising their long-term outcome in terms of disease-free survival, then this conservative approach is warranted.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid hormone-induced dopamine turnover in the rat medial basal hypothalamus

The parathyroid hormone (PTH) gene is expressed and translated in the rat hypothalamus, and the possibility that PTH may modulate neural activity was therefore examined in anesthetized rats. Intracerebroventricular (ICV) injections of 1.0 or 10.0 micrograms rat, human, or bovine PTH(1-34) was followed 60 min later by increased concentrations of DOPAC (dihydroxyacetic acid) and the DOPAC:dopamine (DA) ratio in the medial basal hypothalamus (MBH), but not in other (brainstem, cerebral cortex, cerebellum) regions of the brain. Tissue concentrations of norepinephrine and serotonin were unchanged by ICV PTH administration, although MBH concentrations of 5-hydroxyindolacetic acid (5-HIAA) were increased following PTH administration. An increase in MBH DA turnover (as indicated by an increased DOPAC:DA ratio) was also induced by the ICV injection of 10 micrograms PTH-related protein [PTHrP(1-34)]. Pretreatment with the receptor antagonists PTH(7-34) or PTHrP(7-34) completely blocked the subsequent DOPAC response to ICV PTH or PTHrP, respectively. The DOPAC concentrations in hypothalamic extracellular fluid (ECF), sampled by microdialysis, were also increased within 20 min of PTH(1-34) perfusion, in the absence of changes in the ECF concentrations of 5-HIAA. These results demonstrate that PTH and PTH-like peptides specifically increase DA turnover in the rat MBH and suggest novel roles for these hormones in neural regulation.

Dopaminergic actions of parathyroid hormone in the rat medial basal hypothalamus in vitro

Parathyroid hormone (PTH) modulates dopamine (DA) metabolism in the rat medial basal hypothalamus (MBH) in vivo. Direct effects of PTH on MBH DA metabolism were therefore investigated in vitro. Incubation of rat MBHs for 60 min with 10(-7)-10(-5) M human PTH1-34 consistently reduced the tissue DA content and increased the DOPAC (dihydroxyphenylacetic acid) to DA ratio. This ratio was further increased in tissues incubated in 10(-5) M PTH1-34, as a result of an increase in DOPAC content. The tissue content of DOPAC and DA was unaffected by 10(-9) M PTH. The serotonin (5HT) content of the MBH was reduced by 10(-5) M PTH1-34, but concentrations of 5HT, 5-hydroxyindolacetic acid, and norepinephrine were otherwise unaffected by 10(-9)-10(-5) M PTH1-34. Concentrations of DA in the incubation media were reduced after exposure to 10(-6) or 10(-5) M PTH1-34. The uptake of 3H-labelled DA by incubated tissues was also reduced by 10(-6) M PTH1-34, as was the metabolism of 3H-labelled DA into tissue and media DOPAC. Monoamine oxidase (MAO) activities A and B were significantly increased after the incubation of the MBH with 10(-6) or 10(-5) M PTH1-34. These results further demonstrate neuromodulatory actions of PTH on dopaminergic neurons within the rat MBH in vitro, and suggest neural and/or neuroendocrine roles of PTH of central or peripheral origin.

Effect of 1,25-dihydroxyvitamin D3 and nifedipine on prolactin release in normal man

In normal man 1,25 (OH)2-vitamin D3 [1,25 (OH)2D] increases both basal and TRH-stimulated prolactinemia; this effect is completely reversible by the calcium antagonist nifedipine. Similarly the 1,25 (OH)2D-induced hypercalcemia is totally inhibited by nifedipine. These findings suggest that both biological effects of 1,25 (OH)2D are mediated by calcium-dependent mechanisms.

Prolactin and calcium metabolism: influence of hyperprolactinemia on immunoreactive parathyroid hormone levels in man and in the rat

Serum prolactin, parathyroid hormone, P and Ca serum levels were measured in 15 patients (12 women and 3 men) with hyperprolactinemia, and in 6 normal male volunteers who underwent a TRH test (100 micrograms by rapid iv injection) in order to obtain a short-term pharmacologically-induced hyperprolactinemia. A pituitary gland graft under the kidney capsule was carried out on 26 Sprague-Dawley male rats, which became hyperprolactinemic since the transplanted pituitary was stripped of the inhibitory hypothalamic control. Another group of 10 rats was injected with L-sulpiride (0.1 mg/kg). The serum PTH levels in patients and in subjects with induced hyperprolactinemia were within the normal range and there was no correlation between serum PRL and PTH levels. The same occurred both in transplanted and L-sulpiride injected rats. Our results suggest that prolactin does not modify PTH secretion in vivo and therefore, in contrast with previous data, it should not be considered a physiologically relevant secretagogue for parathyroid hormone.