In 1964, Drs. Smith, Lemli and Opitz (1) recognized that facial malformations, polydactyly of hands or feet, congenital heart defects, ambiguous genitalia and renal pulmonary, liver, and eye abnormalities. all seemed to occur in a slect group of infants. They proposed that this collection of symptoms comprised a syndrome, which today is commonly deignated as SLO syndrome.
In 1984, Chasalow, Blethen and Taysi (2) investigated a child with the malformations typical of SLO syndrome but who also had both potassium wasting and high levels of 17-hydroxyprogesterone. This pattern had not previously been reported. The infant had ambiguous genitalia and had high levels of steroids that cross-reacted with some, but not all, antibodies specific for dehydroepiandrosterone-sulfate (DHEA-S). Extraction and chromatography showed there were two unknown steroids present. We collected serum from infants of similar age and repeated the chromatography. There were four peaks. Thus, we had several new findings:  during the first week of life, infants have 4 unidentified compounds present in their serum,  the compounds are not present by the second week of post-natal life, and  infants with SLO syndrome had only two of the unknown compounds.
Our laboratory had developed a method to recognize carriers for 21-hydroxylase deficiency by monitoring the 17-hydroxyprogesterone response to ACTH after overnight dexamethsaone suppression (3). The parents of our affected patient also had a positive response. This seemed to confirm that this was a biochemical defect but its identity was unknown. There were no steps in classical steroid biosynthesis that matched SLO syndrome. A review of case reports noted that the infants benefited from digoxin therapy. Our patient benefited from digoxin therapy but did not survive. My thought was that the missing hormone might be responsible for potassium saving, but no endogenous hormone with that function was known.
In 1984, we moved to Schneider Children's Hospital, a part of Long Island Jewish Medical Center. I rejoined colleagues from the NYC Steroid Journal Club. During 'liver' rounds I discussed the SLO syndrome data with Dr. Leon Bradlow. He said he was investigating human breast cyst fluids and some were rich in potassium. We thought the two observations were related- one was a deficiency and one was a surplus of a potassium sparing hormone. This was the key observation that provided a rich source from which to isolate the proposed hormone. Meanwhile....
In 1991, from 80 L of human plasma and by monitoring samples on the basis of cross reactivity with a digoxin-specific antibody, Hamlyn (4) isolated 13 ug of a ouabain-like material. In 1993, Irons (5) reported that patients with SLO had a defect in cholesterol biosynthesis, specifically, 7-dehydrosterol reductase deficiency. Neither group recognized that, the compound that Hamlyn isolated, might be defective in SLO patients and might account for some of the symptoms of SLO syndrome. To test this hypothesis, digoxin (labeled with tritium) was added to serum and extracted as we had done before. Although we recovered unlabeled DLM, it was not labeled with the tritiated digoxin. Whatever it was that we detected with the DLM assay, it was not digoxin. A similar investigation confirmed it was not ouabain.
In 2016, Chasalow (6) reported the isolation of steroid phosphoester conjugates from porcine blood and bovine adrenals. Four compounds were isolated; three were spiral steroids with 23 carbon atoms and one was a 21 carbon compound. The mass ions from the 21-carbon compound and from one of the spiral steroids were consistent with a 5-7 diene derivative.
We concluded that in addition to the malformations dependent on cholesterol deficiency, some of the symptoms characteristic of SLO could be caused by the inability to metabolize the 7-dehydrosterol intermediate to the active spiral steroid hormones.
Smith DW, Lemli L, Opitz M. A newly recognized syndrome of multiple congenital anomalies. J Pediatrics. 64: 210-217 (1964). Pubmed/14119520.
Chasalow F, Blethen S, Taysi K. Possible abnormalities of steroid secretion in children with Smith-Lemli-Opitz syndrome and their parents. Steroids. 46: 827-843 (1985).
Granoff A, Chasalow F, Blethen S. 17-hydroxyprogesteroneresponse to ACTH in children with premature Adrenarche. J Endocrinol Metab. (1985) 60: 409-415.
Hamlyn J, Blaustein M, Bova S, DuCharme D, Harris D, Mandel F, Mathews W, Ludens J. Identification and characterization of a ouabain-like compound from human plasma. Proc Natl Acad Sci. 88: 6259-6263 (1991).
Irons M, Elias E, Salen G, Tint G, Batta A. Defective cholesterol synthesis in the Smith-Lemli-Opitz syndrome. Lancet 341: 141 (1993).
Chasalow F, Pierce-Cohen L. Ionotropin is the mammalian digoxin-like material (DLM). It is a phosphocholine ester of a steroid with 23 carbon atoms. Steroids. 2018 Mar 14; PubMed PMID: 29550540. doi.org/10.1016/j.steroids.2018.03.001
Chasalow F, Blethen S. On the consequences of 7-dehydrosterol reductase deficiency (SLO Syndrome). Presented at the Endocrine Society Meeting, Boston. (2016) SUN 229. doi: 10.13140/RG.2.1.3107.8800.