In a study on the maternity records of 5750 Hausa women living in the Savannah zone of Nigeria, there were 40 twins and 2 triplets per 1000 births. Twenty-six percent of twins were monozygotic. The incidence of multiple births, which was about five times higher than that observed in any western population, was significantly lower than that of other ethnic groups, who live in the hot and humid climate of the southern part of the country. The incidence of multiple births was related to maternal age but did not bear any association to the climate or prevalence of malaria.Twins are more common in people of African descent. Predisposing factors
The predisposing factors of monozygotic twinning are unknown. Dizygotic twin pregnancies are slightly more likely when the following factors are present in the woman:

She is of West African descent (especially Yoruba)
She is between the age of 30 and 40 years
She is greater than average height and weight
She has had several previous pregnancies.Women undergoing certain fertility treatments may have a greater chance of dizygotic multiple births. In the United States it has been estimated that by 2011 36% of twin births resulted from conception by assisted reproductive technology.The risk of twin birth can vary depending on what types of fertility treatments are used. With in vitro fertilisation (IVF), this is primarily due to the insertion of multiple embryos into the uterus. Ovarian hyperstimulation without IVF has a very high risk of multiple birth.
Tiopronin, sold under the brand name Thiola, is a medication used to control the rate of cystine precipitation and excretion in the disease cystinuria. Due to the rarity of the disorder, tiopronin falls under the classification of an orphan drug. It is somewhat similar to penicillamine in both chemistry and pharmacology.A generic version of tiopronin is available in the United States as of April 2021. Uses
Tiopronin is used primarily for cystinuria and is well known in the cystinuric community. Depending on the severity of a persons cystinuria, tiopronin may be taken for life, possibly starting in early childhood. The drug works by reacting with urinary cysteine to form a more soluble, disulfide linked, tiopronin-cysteine complex. Side effects
Tiopronin may present a variety of side effects, which are broadly similar to those of D-penicillamine and other compounds containing active sulfhydryl groups. Its pharmacokinetics have been studied. Society and culture
In the U.S., the drug was marketed by Mission Pharmacal at $1.50 per pill, but in 2014 the rights were bought by Retrophin, owned by Martin Shkreli, and the price increased to $30 per pill for a 100 mg capsule.In 2016 Imprimis Pharmaceuticals introduced a lower cost version marketed as a compounded drug. Research
It may also be used for Wilsons disease (an overload of copper in the body), and has also been investigated for the treatment of arthritis, though tiopronin is not an anti-inflammatory.Tiopronin is also sometimes used as a stabilizing agent for metal nanoparticles. The thiol group binds to the nanoparticles, preventing coagulation. References
External links
"Tiopronin". Drug Information Portal.