Effect of lithium carbonate on the function of the thyroid gland: mechanism of action and clinical implications

Lithium carbonate, a drug known for more than 100 years, has been successfully used as a psychiatric medication. Currently, it is a commonly used drug to treat patients with unipolar and bipolar depression, and for the prophylaxis of bipolar disorders and acute mania. Lithium salts may cause the development of goiter, hypothyroidism, or rarely hyperthyroidism. The present review examined the current state of knowledge on the effect of lithium carbonate on the thyroid gland. The Pubmed database and Google Scholar were searched for articles related to the effects of lithium therapy on the thyroid gland function published up to February 2020. Studies that examined the mechanism of action of lithium at the molecular level, including pharmacokinetics, and focused on its effects on the thyroid gland were included. Lithium as a mood-stabilizing drug has a complex mechanism of action. Because of the active transport of Na⁺/I^- ions, lithium, despite its concentration gradient, is accumulated in the thyroid gland at a concentration 3 - 4 times higher than that in the plasma. It can inhibit the formation of colloid in thyrocytes, change the structure of thyroglobulin, weaken the iodination of tyrosines, and disrupt their coupling. In addition, it reduces the clearance of free thyroxine in the serum, thereby indirectly reducing the activity of 5-deiodinase type 1 and 2 and reducing the deiodination of these hormones in the liver. Taken together, this review provides recommendations for monitoring the thyroid gland in patients who require long-term lithium therapy. Prior to the initiation of lithium therapy, thyroid ultrasound should be performed, and the levels of thyroid hormones (fT3 and fT4), TSH, and antithyroid peroxidase and antithyroglobulin antibodies should be measured. If the patient shows normal thyroid function, TSH level measurement and thyroid ultrasound should be performed at 6- to 12-month intervals for long term.

Risk of malignant neoplasms in acromegaly: a case-control study

PURPOSE

Acromegaly is a chronic disease resulting from pathological oversecretion of growth hormone and subsequently insulin growth factor-1. Several complications of the disease have been reported, including cardiovascular diseases, respiratory disorders but also increased risk of benign and malignant neoplasms. The aim of the study was to evaluate the risk of malignant neoplasms in the patients with acromegaly in comparison with the control group.

PATIENTS AND METHODS

Medical documentation of acromegalic patients treated in one medical center between 2005 and 2016 has been analyzed. Results were compared with sex- and age-matched group of subjects with prolactinomas and hormonally inactive pituitary lesions hospitalized in the same department.

RESULTS

Two hundred patients with acromegaly were included. Control group was composed of 145 patients. Any malignant neoplasm in anamnesis was present in 27 (13.5 %) patients with acromegaly and six (4.1 %) subjects from control group (p = 0.003). Thyroid cancer was present in 14 (7.0 %) patients with acromegaly and two (1.4 %) in control group (p = 0.02). Breast cancer was present in seven women (5.4 % of women) in acromegaly group but none of subjects in control group (p = 0.02). Colon cancer-4 (2.0 %) patients in acromegaly group and 0 in control group (p = 0.14).

CONCLUSIONS

Malignant neoplasms are significantly more common in patients with acromegaly. Particularly, risk of thyroid cancer was increased over fivefold. Systematic screening for neoplastic diseases should be important part of follow-up in these patients. Further case-control studies are strongly indicated to evaluate which neoplasms are more common in acromegalic patients and what is the exact risk of malignancy.

Cushing's syndrome in pregnancy: a case report and mini review of the literature

Adrenal diseases in pregnant women are diagnosed relatively rarely. The main cause of hypercortisolemia during pregnancy is Cushing's syndrome related to adrenal adenoma. It is important to diagnose Cushing's syndrome in pregnant women because it can lead to significant maternal and foetal complications and morbidity. However, due to physiological endocrine changes and symptoms in pregnant women the diagnosis of this disorder can be a challenge. One current case describes a 38-year-old pregnant woman with hypertension, oedema and an adrenal tumour. At the beginning, Conn syndrome was suspected, but after careful analysis Cushing's syndrome (with an adenoma of the right adrenal gland) was diagnosed. After delivery and 5 weeks of pharmacological treatment the patient underwent right side adrenalectomy by laparoscopy.

Increased serum osteoprotegerin in patients with primary adrenal insufficiency receiving conventional hydrocortisone substitution

Patients treated for primary adrenal insufficiency (PAI) are at risk of steroid over-replacement, which may affect their skeleton. The study was aimed to investigate the effect of steroid substitution on serum osteoprotegerin and receptor activator of nuclear factor kappa-beta ligand (RANKL) levels in relation to bone mineral density (BMD) in PAI. Eighty patients (mean age 47.2±14.5 years, mean hydrocortisone dose 0.49±0.14 mg/kg/day) and 63 healthy subjects were included. Serum osteoprotegerin, RANKL, 25-hydroxyvitamin D₃, calcium, phosphate, alkaline phosphatase, intact parathormone, and dehydroepiandrosterone-sulfate levels were evaluated in patients and controls. BMD was assessed in affected subjects using dual-energy X-ray absorptiometry. Mean osteoprotegerin concentration in PAI patients appeared significantly higher vs. controls (p=0.002), while RANKL levels were similar (p=0.430). Serum osteoprotegerin increased with age (p<0.001), but showed no correlation with daily hydrocortisone dose. Osteoprotegerin was negatively correlated with serum dehydroepiandrosterone-sulfate (p=0.008) and with BMD at the lumbar spine (p<0.001) and femoral neck (p=0.003). RANKL correlated negatively with PAI duration (p=0.029) and positively with daily hydrocortisone dose (p=0.018). Lumbar spine osteoporosis and osteopenia were found in 12 and 31 patients, respectively, whereas in femoral neck: in 5 and 33 individuals. Patients with osteoporosis displayed higher osteoprotegerin levels, but after the age-adjustment the correlation was lost. In conclusion, increased osteoprotegerin in PAI might reflect a compensatory response to enhanced bone resorption due to exogenous steroid excess and/or result from a deficit in adrenal androgens. RANKL levels remain within normal range on standard steroid replacement.